diff --git a/src/command-line-parser.cpp b/src/command-line-parser.cpp
index f5d96f059..568d9f5f5 100644
--- a/src/command-line-parser.cpp
+++ b/src/command-line-parser.cpp
@@ -14,6 +14,7 @@
 #include "logging.hpp"
 #include "options.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "reprojection.hpp"
 #include "util.hpp"
 #include "version.hpp"
@@ -244,7 +245,7 @@ void check_options_expire(options_t *options) {
     }
 
     if (options->expire_tiles_zoom != 0 &&
-        options->projection->target_srs() != 3857) {
+        options->projection->target_srs() != PROJ_SPHERE_MERC) {
         log_warn("Expire has been enabled (with -e or --expire-tiles) but "
                  "target SRS is not Mercator (EPSG:3857). Expire disabled!");
         options->expire_tiles_zoom = 0;
diff --git a/src/expire-tiles.cpp b/src/expire-tiles.cpp
index 21eda2df7..d2325f9a1 100644
--- a/src/expire-tiles.cpp
+++ b/src/expire-tiles.cpp
@@ -28,6 +28,7 @@
 #include "format.hpp"
 #include "geom-functions.hpp"
 #include "options.hpp"
+#include "projection.hpp"
 #include "reprojection.hpp"
 #include "table.hpp"
 #include "tile.hpp"
@@ -146,7 +147,7 @@ void expire_tiles::from_geometry(geom::geometry_t const &geom,
 void expire_tiles::from_geometry_if_3857(geom::geometry_t const &geom,
                                          expire_config_t const &expire_config)
 {
-    if (geom.srid() == 3857) {
+    if (geom.srid() == PROJ_SPHERE_MERC) {
         from_geometry(geom, expire_config);
     }
 }
diff --git a/src/flex-lua-geom.cpp b/src/flex-lua-geom.cpp
index ed48b5da3..4fc2880ee 100644
--- a/src/flex-lua-geom.cpp
+++ b/src/flex-lua-geom.cpp
@@ -12,6 +12,7 @@
 #include "geom-functions.hpp"
 #include "geom-pole-of-inaccessibility.hpp"
 #include "lua-utils.hpp"
+#include "projection.hpp"
 
 #include <lua.hpp>
 
@@ -73,7 +74,7 @@ int geom_spherical_area(lua_State *lua_state)
 {
     auto const *const input_geometry = unpack_geometry(lua_state);
 
-    if (input_geometry->srid() != 4326) {
+    if (input_geometry->srid() != PROJ_LATLONG) {
         throw std::runtime_error{"Can only calculate spherical area for "
                                  "geometries in WGS84 (4326) coordinates."};
     }
@@ -282,7 +283,7 @@ int geom_transform(lua_State *lua_state)
     auto const srid = static_cast<int>(luaL_checkinteger(lua_state, 2));
 
     try {
-        if (input_geometry->srid() != 4326) {
+        if (input_geometry->srid() != PROJ_LATLONG) {
             throw std::runtime_error{
                 "Can not transform already transformed geometry."};
         }
diff --git a/src/flex-lua-table.cpp b/src/flex-lua-table.cpp
index 3a41bcc1e..d7239706a 100644
--- a/src/flex-lua-table.cpp
+++ b/src/flex-lua-table.cpp
@@ -16,6 +16,7 @@
 #include "lua-utils.hpp"
 #include "output-flex.hpp"
 #include "pgsql-capabilities.hpp"
+#include "projection.hpp"
 #include "util.hpp"
 
 #include <lua.hpp>
@@ -219,7 +220,7 @@ void parse_and_set_expire_options(lua_State *lua_state,
         return;
     }
 
-    if (!column->is_geometry_column() || column->srid() != 3857) {
+    if (!column->is_geometry_column() || column->srid() != PROJ_SPHERE_MERC) {
         throw std::runtime_error{"Expire only allowed for geometry"
                                  " columns in Web Mercator projection."};
     }
diff --git a/src/flex-table-column.cpp b/src/flex-table-column.cpp
index 3ba3c4b67..57ed471ff 100644
--- a/src/flex-table-column.cpp
+++ b/src/flex-table-column.cpp
@@ -11,6 +11,7 @@
 
 #include "format.hpp"
 #include "pgsql-capabilities.hpp"
+#include "projection.hpp"
 #include "util.hpp"
 
 #include <cassert>
@@ -105,12 +106,12 @@ void flex_table_column_t::set_projection(char const *projection)
     auto const proj = lowercase(projection);
 
     if (proj == "merc" || proj == "mercator") {
-        m_srid = 3857;
+        m_srid = PROJ_SPHERE_MERC;
         return;
     }
 
     if (proj == "latlong" || proj == "latlon" || proj == "wgs84") {
-        m_srid = 4326;
+        m_srid = PROJ_LATLONG;
         return;
     }
 
@@ -197,7 +198,7 @@ std::string flex_table_column_t::sql_create() const
 void flex_table_column_t::add_expire(expire_config_t const &config)
 {
     assert(is_geometry_column());
-    assert(srid() == 3857);
+    assert(srid() == PROJ_SPHERE_MERC);
     m_expires.push_back(config);
 }
 
diff --git a/src/flex-table-column.hpp b/src/flex-table-column.hpp
index 4d445ed71..d19edef5b 100644
--- a/src/flex-table-column.hpp
+++ b/src/flex-table-column.hpp
@@ -13,6 +13,7 @@
 #include "expire-config.hpp"
 #include "expire-tiles.hpp"
 #include "geom.hpp"
+#include "projection.hpp"
 
 #include <cassert>
 #include <cstdint>
@@ -99,7 +100,7 @@ class flex_table_column_t
     bool needs_isvalid() const noexcept
     {
         assert(is_geometry_column());
-        return !m_create_only && m_srid != 4326 &&
+        return !m_create_only && m_srid != PROJ_LATLONG &&
                m_type != table_column_type::point;
     }
 
@@ -158,7 +159,7 @@ class flex_table_column_t
     /**
      * For geometry columns only: The projection SRID. Default is web mercator.
      */
-    int m_srid = 3857;
+    int m_srid = PROJ_SPHERE_MERC;
 
     /// NOT NULL constraint
     bool m_not_null = false;
diff --git a/src/flex-table.hpp b/src/flex-table.hpp
index d5bd5198f..489496bf2 100644
--- a/src/flex-table.hpp
+++ b/src/flex-table.hpp
@@ -14,6 +14,7 @@
 #include "flex-index.hpp"
 #include "flex-table-column.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "reprojection.hpp"
 #include "thread-pool.hpp"
 #include "util.hpp"
@@ -145,7 +146,7 @@ class flex_table_t
 
     int srid() const noexcept
     {
-        return has_geom_column() ? geom_column().srid() : 4326;
+        return has_geom_column() ? geom_column().srid() : PROJ_LATLONG;
     }
 
     std::string build_sql_prepare_get_wkb() const;
diff --git a/src/gen/gen-rivers.cpp b/src/gen/gen-rivers.cpp
index 54aaba8ef..111291738 100644
--- a/src/gen/gen-rivers.cpp
+++ b/src/gen/gen-rivers.cpp
@@ -14,6 +14,7 @@
 #include "logging.hpp"
 #include "params.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "util.hpp"
 #include "wkb.hpp"
 
@@ -341,7 +342,7 @@ SELECT "{id_column}", "{width_column}", "{name_column}", "{geom_column}"
     timer(m_timer_write).start();
     connection().exec("BEGIN");
     for (auto &edge : edges) {
-        geom::geometry_t const geom{std::move(edge.points), 3857};
+        geom::geometry_t const geom{std::move(edge.points), PROJ_SPHERE_MERC};
         auto const wkb = geom_to_ewkb(geom);
         connection().exec_prepared("ins", edge.id, edge.width,
                                    get_name(names, edge.id), binary_param(wkb));
diff --git a/src/gen/raster.hpp b/src/gen/raster.hpp
index 8708789a2..c1cf895bc 100644
--- a/src/gen/raster.hpp
+++ b/src/gen/raster.hpp
@@ -10,6 +10,8 @@
  * For a full list of authors see the git log.
  */
 
+#include "projection.hpp"
+
 #include <cstdint>
 #include <string>
 
@@ -41,7 +43,7 @@ struct wkb_raster_header
     double ipY = 0.0;
     double skewX = 0.0;
     double skewY = 0.0;
-    int32_t srid = 3857;
+    int32_t srid = PROJ_SPHERE_MERC;
     uint16_t width = 0;
     uint16_t height = 0;
 };
diff --git a/src/gen/tracer.cpp b/src/gen/tracer.cpp
index 7f9eb9296..b8e54826e 100644
--- a/src/gen/tracer.cpp
+++ b/src/gen/tracer.cpp
@@ -11,6 +11,7 @@
 
 #include "canvas.hpp"
 #include "geom-boost-adaptor.hpp"
+#include "projection.hpp"
 #include "tile.hpp"
 
 #include <cassert>
@@ -114,7 +115,7 @@ tracer_t::build_geometries(tile_t const &tile, potrace_path_t const *plist,
             m_num_points += ring.size();
 
             if (path->sign == '+') {
-                geometries.emplace_back(geom::polygon_t{}, 3857)
+                geometries.emplace_back(geom::polygon_t{}, PROJ_SPHERE_MERC)
                     .get<geom::polygon_t>()
                     .outer() = std::move(ring);
             } else {
diff --git a/src/geom-functions.cpp b/src/geom-functions.cpp
index a6db4c9ca..369f9f32c 100644
--- a/src/geom-functions.cpp
+++ b/src/geom-functions.cpp
@@ -11,6 +11,7 @@
 
 #include "geom-boost-adaptor.hpp"
 #include "overloaded.hpp"
+#include "projection.hpp"
 
 #include <algorithm>
 #include <cmath>
@@ -228,7 +229,7 @@ class transform_visitor
 void transform(geometry_t *output, geometry_t const &input,
                reprojection const &reprojection)
 {
-    assert(input.srid() == 4326);
+    assert(input.srid() == PROJ_LATLONG);
 
     set_to_same_type(output, input);
     output->set_srid(reprojection.target_srs());
@@ -385,7 +386,7 @@ double spherical_area(polygon_t const &geom)
 
 double spherical_area(geometry_t const &geom)
 {
-    assert(geom.srid() == 4326);
+    assert(geom.srid() == PROJ_LATLONG);
 
     return std::abs(geom.visit(overloaded{
         [&](geom::nullgeom_t const & /*input*/) { return 0.0; },
diff --git a/src/geom.hpp b/src/geom.hpp
index 250f88081..ac71c7653 100644
--- a/src/geom.hpp
+++ b/src/geom.hpp
@@ -16,6 +16,8 @@
  * Basic geometry types and functions.
  */
 
+#include "projection.hpp"
+
 #include <osmium/osm/location.hpp>
 
 #include <algorithm>
@@ -274,31 +276,33 @@ class geometry_t
 
     // point_t is small and trivially copyable, no move needed like for the
     // other constructors.
-    constexpr explicit geometry_t(point_t geom, int srid = 4326)
+    constexpr explicit geometry_t(point_t geom, int srid = PROJ_LATLONG)
     : m_geom(geom), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(linestring_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(linestring_t &&geom, int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(polygon_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(polygon_t &&geom, int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(multipoint_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(multipoint_t &&geom, int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(multilinestring_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(multilinestring_t &&geom,
+                                  int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(multipolygon_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(multipolygon_t &&geom,
+                                  int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(collection_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(collection_t &&geom, int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
@@ -397,7 +401,7 @@ class geometry_t
                  multilinestring_t, multipolygon_t, collection_t>
         m_geom = nullgeom_t{};
 
-    int m_srid = 4326;
+    int m_srid = PROJ_LATLONG;
 
 }; // class geometry_t
 
diff --git a/src/locator.cpp b/src/locator.cpp
index 844eae364..73e49ef87 100644
--- a/src/locator.cpp
+++ b/src/locator.cpp
@@ -16,6 +16,7 @@
 #include "overloaded.hpp"
 #include "pgsql-capabilities.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "wkb.hpp"
 
 #include <iterator>
@@ -63,7 +64,7 @@ void locator_t::add_regions(pg_conn_t const &db_connection,
         std::string const name = result.get_value(n, 0);
         auto geometry = ewkb_to_geom(util::decode_hex(result.get(n, 1)));
 
-        if (geometry.srid() == 4326) {
+        if (geometry.srid() == PROJ_LATLONG) {
             add_region(name, geometry);
         } else {
             log_warn("Ignoring locator geometry that is not in WGS84 (4326)");
diff --git a/src/output-flex.cpp b/src/output-flex.cpp
index 1428f102f..197d77937 100644
--- a/src/output-flex.cpp
+++ b/src/output-flex.cpp
@@ -33,6 +33,7 @@
 #include "osmtypes.hpp"
 #include "pgsql-capabilities.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "properties.hpp"
 #include "reprojection.hpp"
 #include "thread-pool.hpp"
@@ -1191,8 +1192,9 @@ output_flex_t::output_flex_t(output_flex_t const *other,
     }
 
     for (auto &expire_output : *m_expire_outputs) {
-        m_expire_tiles.emplace_back(expire_output.maxzoom(),
-                                    reprojection::create_projection(3857));
+        m_expire_tiles.emplace_back(
+            expire_output.maxzoom(),
+            reprojection::create_projection(PROJ_SPHERE_MERC));
     }
 }
 
@@ -1235,7 +1237,8 @@ output_flex_t::output_flex_t(std::shared_ptr<middle_query_t> const &mid,
         eo.set_maxzoom(options.expire_tiles_zoom);
 
         for (auto &table : *m_tables) {
-            if (table.has_geom_column() && table.geom_column().srid() == 3857) {
+            if (table.has_geom_column() &&
+                table.geom_column().srid() == PROJ_SPHERE_MERC) {
                 expire_config_t config{};
                 config.expire_output = m_expire_outputs->size() - 1;
                 if (options.expire_tiles_max_bbox > 0.0) {
@@ -1255,8 +1258,9 @@ output_flex_t::output_flex_t(std::shared_ptr<middle_query_t> const &mid,
     }
 
     for (auto &expire_output : *m_expire_outputs) {
-        m_expire_tiles.emplace_back(expire_output.maxzoom(),
-                                    reprojection::create_projection(3857));
+        m_expire_tiles.emplace_back(
+            expire_output.maxzoom(),
+            reprojection::create_projection(PROJ_SPHERE_MERC));
     }
 
     create_expire_tables(*m_expire_outputs, get_options()->connection_params);
diff --git a/src/output-pgsql.cpp b/src/output-pgsql.cpp
index 51b078d8d..8167645d4 100644
--- a/src/output-pgsql.cpp
+++ b/src/output-pgsql.cpp
@@ -38,6 +38,7 @@
 #include "osmtypes.hpp"
 #include "output-pgsql.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "reprojection.hpp"
 #include "taginfo-impl.hpp"
 #include "tagtransform.hpp"
@@ -51,7 +52,7 @@ double calculate_area(bool reproject_area, geom::geometry_t const &geom4326,
                       geom::geometry_t const &projected_geom)
 {
     static thread_local auto const proj3857 =
-        reprojection::create_projection(3857);
+        reprojection::create_projection(PROJ_SPHERE_MERC);
 
     if (reproject_area) {
         auto const ogeom = geom::transform(geom4326, *proj3857);
diff --git a/src/projection.hpp b/src/projection.hpp
new file mode 100644
index 000000000..b3230039a
--- /dev/null
+++ b/src/projection.hpp
@@ -0,0 +1,16 @@
+#ifndef OSM2PGSQL_PROJECTION_HPP
+#define OSM2PGSQL_PROJECTION_HPP
+
+/**
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This file is part of osm2pgsql (https://osm2pgsql.org/).
+ *
+ * Copyright (C) 2006-2025 by the osm2pgsql developer community.
+ * For a full list of authors see the git log.
+ */
+
+constexpr int PROJ_LATLONG = 4326;
+constexpr int PROJ_SPHERE_MERC = 3857;
+
+#endif // OSM2PGSQL_PROJECTION_HPP
diff --git a/src/reprojection.hpp b/src/reprojection.hpp
index 50d17e65a..e1de8c90f 100644
--- a/src/reprojection.hpp
+++ b/src/reprojection.hpp
@@ -17,16 +17,11 @@
  */
 
 #include "geom.hpp"
+#include "projection.hpp"
 
 #include <memory>
 #include <string>
 
-enum Projection
-{
-    PROJ_LATLONG = 4326,
-    PROJ_SPHERE_MERC = 3857
-};
-
 /**
  * Virtual base class used for projecting OSM WGS84 coordinates into a
  * different coordinate system. Most commonly this will be used to convert
diff --git a/tests/test-expire-from-geometry.cpp b/tests/test-expire-from-geometry.cpp
index ae5f5f532..f0c73c47f 100644
--- a/tests/test-expire-from-geometry.cpp
+++ b/tests/test-expire-from-geometry.cpp
@@ -13,6 +13,7 @@
 #include <set>
 
 #include "expire-tiles.hpp"
+#include "projection.hpp"
 #include "reprojection.hpp"
 #include "tile-output.hpp"
 #include "tile.hpp"
@@ -42,7 +43,7 @@ TEST_CASE("expire null geometry does nothing", "[NoDB]")
     SECTION("geom with check")
     {
         geom::geometry_t geom{};
-        geom.set_srid(3857);
+        geom.set_srid(PROJ_SPHERE_MERC);
         et.from_geometry_if_3857(geom, expire_config);
     }
 
@@ -67,7 +68,7 @@ TEST_CASE("expire point at tile boundary", "[NoDB]")
     SECTION("geom with check")
     {
         geom::geometry_t geom{pt};
-        geom.set_srid(3857);
+        geom.set_srid(PROJ_SPHERE_MERC);
         et.from_geometry_if_3857(geom, expire_config);
     }
 
@@ -97,7 +98,7 @@ TEST_CASE("expire point away from tile boundary", "[NoDB]")
     SECTION("geom with check")
     {
         geom::geometry_t geom{pt};
-        geom.set_srid(3857);
+        geom.set_srid(PROJ_SPHERE_MERC);
         et.from_geometry_if_3857(geom, expire_config);
     }
 
@@ -128,7 +129,7 @@ TEST_CASE("expire linestring away from tile boundary", "[NoDB]")
     {
         geom::linestring_t line{{5000.0, 4000.0}, {5100.0, 4200.0}};
         geom::geometry_t geom{std::move(line)};
-        geom.set_srid(3857);
+        geom.set_srid(PROJ_SPHERE_MERC);
         et.from_geometry_if_3857(geom, expire_config);
     }
 
@@ -159,7 +160,7 @@ TEST_CASE("expire linestring crossing tile boundary", "[NoDB]")
     {
         geom::linestring_t line{{5000.0, 5000.0}, {5000.0, 15000.0}};
         geom::geometry_t geom{std::move(line)};
-        geom.set_srid(3857);
+        geom.set_srid(PROJ_SPHERE_MERC);
         et.from_geometry_if_3857(geom, expire_config);
     }
 
@@ -203,7 +204,7 @@ TEST_CASE("expire small polygon", "[NoDB]")
                               {5000.0, 5100.0},
                               {5000.0, 5000.0}}};
         geom::geometry_t geom{std::move(poly)};
-        geom.set_srid(3857);
+        geom.set_srid(PROJ_SPHERE_MERC);
         et.from_geometry_if_3857(geom, expire_config);
     }
 
@@ -248,7 +249,7 @@ TEST_CASE("expire large polygon as bbox", "[NoDB]")
                               {5000.0, 25000.0},
                               {5000.0, 5000.0}}};
         geom::geometry_t geom{std::move(poly)};
-        geom.set_srid(3857);
+        geom.set_srid(PROJ_SPHERE_MERC);
         et.from_geometry_if_3857(geom, expire_config);
     }
 
@@ -313,7 +314,7 @@ TEST_CASE("expire large polygon as boundary", "[NoDB]")
                               {5000.0, 25000.0},
                               {5000.0, 5000.0}}};
         geom::geometry_t geom{std::move(poly)};
-        geom.set_srid(3857);
+        geom.set_srid(PROJ_SPHERE_MERC);
         et.from_geometry_if_3857(geom, expire_config);
     }
 
@@ -362,7 +363,7 @@ TEST_CASE("expire multipoint geometry", "[NoDB]")
         mpt.add_geometry(p1);
         mpt.add_geometry(p2);
         geom::geometry_t geom{std::move(mpt)};
-        geom.set_srid(3857);
+        geom.set_srid(PROJ_SPHERE_MERC);
         et.from_geometry_if_3857(geom, expire_config);
     }
 
@@ -485,7 +486,7 @@ TEST_CASE("expire works if in 3857", "[NoDB]")
     expire_tiles et{zoom, defproj};
 
     geom::geometry_t geom{geom::point_t{0.0, 0.0}};
-    geom.set_srid(3857);
+    geom.set_srid(PROJ_SPHERE_MERC);
     et.from_geometry_if_3857(geom, expire_config);
 
     auto const tiles = et.get_tiles();
diff --git a/tests/test-geom-multilinestrings.cpp b/tests/test-geom-multilinestrings.cpp
index 0ae2e0e63..2fbeb54d9 100644
--- a/tests/test-geom-multilinestrings.cpp
+++ b/tests/test-geom-multilinestrings.cpp
@@ -15,6 +15,7 @@
 #include "geom-functions.hpp"
 #include "geom-output.hpp"
 #include "geom.hpp"
+#include "projection.hpp"
 
 #include <array>
 
@@ -343,7 +344,7 @@ TEST_CASE("create_multilinestring and simplify", "[NoDB]")
         geom::create_multilinestring(buffer.buffer());
 
     REQUIRE(geom.is_multilinestring());
-    REQUIRE(geom.srid() == 4326);
+    REQUIRE(geom.srid() == PROJ_LATLONG);
     auto const &mls = geom.get<geom::multilinestring_t>();
     REQUIRE(mls.num_geometries() == 2);
     REQUIRE(mls[0] == geom::linestring_t{{1, 1}, {1, 2}, {1, 3}});
@@ -353,7 +354,7 @@ TEST_CASE("create_multilinestring and simplify", "[NoDB]")
     {
         auto const simplified_geom = geom::simplify(geom, 0.1);
         REQUIRE(simplified_geom.is_multilinestring());
-        REQUIRE(simplified_geom.srid() == 4326);
+        REQUIRE(simplified_geom.srid() == PROJ_LATLONG);
         auto const &simplified_mls =
             simplified_geom.get<geom::multilinestring_t>();
         REQUIRE(simplified_mls.num_geometries() == 2);
@@ -366,7 +367,7 @@ TEST_CASE("create_multilinestring and simplify", "[NoDB]")
     {
         auto const simplified_geom = geom::simplify(geom, 10.0);
         REQUIRE(simplified_geom.is_multilinestring());
-        REQUIRE(simplified_geom.srid() == 4326);
+        REQUIRE(simplified_geom.srid() == PROJ_LATLONG);
         auto const &simplified_mls =
             simplified_geom.get<geom::multilinestring_t>();
         REQUIRE(simplified_mls.num_geometries() == 2);
diff --git a/tests/test-geom-transform.cpp b/tests/test-geom-transform.cpp
index 8481b1313..10a7ed775 100644
--- a/tests/test-geom-transform.cpp
+++ b/tests/test-geom-transform.cpp
@@ -12,6 +12,7 @@
 #include "geom-functions.hpp"
 #include "geom-output.hpp"
 #include "geom.hpp"
+#include "projection.hpp"
 #include "reprojection.hpp"
 
 namespace {
@@ -47,7 +48,7 @@ TEST_CASE("Transform geom::null_t", "[NoDB]")
     geom::geometry_t const geom{};
     auto const result = geom::transform(geom, *reprojection);
     REQUIRE(result.is_null());
-    REQUIRE(result.srid() == 3857);
+    REQUIRE(result.srid() == PROJ_SPHERE_MERC);
 }
 
 TEST_CASE("Transform geom::point_t", "[NoDB]")
@@ -58,7 +59,7 @@ TEST_CASE("Transform geom::point_t", "[NoDB]")
     geom::geometry_t const geom{geom::point_t{5.5, 4.4}};
     auto const result = geom::transform(geom, *reprojection);
     REQUIRE(result.is_point());
-    REQUIRE(result.srid() == 3857);
+    REQUIRE(result.srid() == PROJ_SPHERE_MERC);
 
     check(result.get<geom::point_t>(),
           geom::point_t{612257.1993630046, 490287.90003313165});
@@ -72,7 +73,7 @@ TEST_CASE("Transform geom::linestring_t", "[NoDB]")
     geom::geometry_t const geom{geom::linestring_t{{5.5, 4.4}, {3.3, 2.2}}};
     auto const result = geom::transform(geom, *reprojection);
     REQUIRE(result.is_linestring());
-    REQUIRE(result.srid() == 3857);
+    REQUIRE(result.srid() == PROJ_SPHERE_MERC);
 
     auto const &r = result.get<geom::linestring_t>();
     check(r[0], geom::point_t{X55, Y44});
@@ -91,7 +92,7 @@ TEST_CASE("Transform geom::polygon_t", "[NoDB]")
 
     auto const result = geom::transform(geom, *reprojection);
     REQUIRE(result.is_polygon());
-    REQUIRE(result.srid() == 3857);
+    REQUIRE(result.srid() == PROJ_SPHERE_MERC);
 
     auto const &polygon = result.get<geom::polygon_t>();
     auto const &outer = polygon.outer();
@@ -125,7 +126,7 @@ TEST_CASE("Transform geom::multipoint_t", "[NoDB]")
 
     auto const result = geom::transform(geom, *reprojection);
     REQUIRE(result.is_multipoint());
-    REQUIRE(result.srid() == 3857);
+    REQUIRE(result.srid() == PROJ_SPHERE_MERC);
 
     auto const &rmp = result.get<geom::multipoint_t>();
     REQUIRE(rmp.num_geometries() == 2);
@@ -145,7 +146,7 @@ TEST_CASE("Transform geom::multilinestring_t", "[NoDB]")
 
     auto const result = geom::transform(geom, *reprojection);
     REQUIRE(result.is_multilinestring());
-    REQUIRE(result.srid() == 3857);
+    REQUIRE(result.srid() == PROJ_SPHERE_MERC);
 
     auto const &rml = result.get<geom::multilinestring_t>();
     REQUIRE(rml.num_geometries() == 2);
@@ -173,7 +174,7 @@ TEST_CASE("Transform geom::multipolygon_t", "[NoDB]")
 
     auto const result = geom::transform(geom, *reprojection);
     REQUIRE(result.is_multipolygon());
-    REQUIRE(result.srid() == 3857);
+    REQUIRE(result.srid() == PROJ_SPHERE_MERC);
 
     auto const &rmp = result.get<geom::multipolygon_t>();
     REQUIRE(rmp.num_geometries() == 2);
@@ -218,7 +219,7 @@ TEST_CASE("Transform geom::collection_t", "[NoDB]")
 
     auto const result = geom::transform(geom, *reprojection);
     REQUIRE(result.is_collection());
-    REQUIRE(result.srid() == 3857);
+    REQUIRE(result.srid() == PROJ_SPHERE_MERC);
 
     auto const &rc = result.get<geom::collection_t>();
     REQUIRE(rc.num_geometries() == 4);
diff --git a/tests/test-reprojection.cpp b/tests/test-reprojection.cpp
index fa14af84a..0818d477c 100644
--- a/tests/test-reprojection.cpp
+++ b/tests/test-reprojection.cpp
@@ -9,12 +9,13 @@
 
 #include <catch.hpp>
 
+#include "projection.hpp"
 #include "reprojection.hpp"
 
 TEST_CASE("projection 4326", "[NoDB]")
 {
     osmium::Location const loc{10.0, 53.0};
-    int const srs = 4326;
+    int const srs = PROJ_LATLONG;
 
     auto const reprojection = reprojection::create_projection(srs);
     REQUIRE(reprojection->target_srs() == srs);
@@ -32,7 +33,7 @@ TEST_CASE("projection 4326", "[NoDB]")
 TEST_CASE("projection 3857", "[NoDB]")
 {
     osmium::Location const loc{10.0, 53.0};
-    int const srs = 3857;
+    int const srs = PROJ_SPHERE_MERC;
 
     auto const reprojection = reprojection::create_projection(srs);
     REQUIRE(reprojection->target_srs() == srs);
@@ -52,7 +53,7 @@ TEST_CASE("projection 3857 bounds", "[NoDB]")
     osmium::Location const loc1{0.0, 0.0};
     osmium::Location const loc2{-180.0, -85.0511288};
     osmium::Location const loc3{180.0, 85.0511288};
-    int const srs = 3857;
+    int const srs = PROJ_SPHERE_MERC;
     auto const reprojection = reprojection::create_projection(srs);
 
     {