diff --git a/bazel/BUILD b/bazel/BUILD
index 4614697cbb..faec6706dd 100644
--- a/bazel/BUILD
+++ b/bazel/BUILD
@@ -1,3 +1,4 @@
+load("@bazel_skylib//rules:build_test.bzl", "build_test")
 load("@openroad_rules_python//python:pip.bzl", "compile_pip_requirements")
 load("@rules_cc//cc:cc_library.bzl", "cc_library")
 
@@ -29,3 +30,11 @@ cc_library(
     ],
     alwayslink = True,
 )
+
+# small build test to check if "bazel build //src/sta:StaTclInitVar" works
+# Run with "bazel test //bazel:sta_tcl_encode_test"
+# Tests the tcl_encode_sta.bzl rule
+build_test(
+    name = "sta_tcl_encode_test",
+    targets = ["//src/sta:StaTclInitVar"],
+)
diff --git a/bazel/tcl_encode_sta.bzl b/bazel/tcl_encode_sta.bzl
index fd5f724ee6..c631a28830 100644
--- a/bazel/tcl_encode_sta.bzl
+++ b/bazel/tcl_encode_sta.bzl
@@ -18,12 +18,23 @@ def _tcl_encode_sta_impl(ctx):
     args.add(ctx.attr.char_array_name)
     args.add_all(ctx.files.srcs)
 
+    # Get the Tcl library files (init.tcl...) from tcl_core
+    tcl_libfiles = ctx.attr._tcl_library_files[DefaultInfo]
+
+    # All tcl_core files live under library/, so split any file's path on
+    # "/library/" to obtain the library directory for TCL_LIBRARY.
+    tcl_lib_dir = ctx.files._tcl_library_files[0].path.split("/library/", 1)[0] + "/library"
+
     ctx.actions.run(
         outputs = [output_file],
-        inputs = ctx.files.srcs,
+        inputs = depset(
+            direct = ctx.files.srcs + [ctx.file._encode_script],
+            transitive = [tcl_libfiles.files],
+        ),
         arguments = [args],
-        tools = [ctx.executable._tclsh, ctx.file._encode_script],
+        tools = [ctx.executable._tclsh],
         executable = ctx.executable._tclsh,
+        env = {"TCL_LIBRARY": tcl_lib_dir},
     )
     return [DefaultInfo(files = depset([output_file]))]
 
@@ -46,6 +57,10 @@ tcl_encode_sta = rule(
             default = "//src/sta:etc/TclEncode.tcl",
             allow_single_file = True,
         ),
+        "_tcl_library_files": attr.label(
+            default = "@tcl_lang//:tcl_core",
+            allow_files = True,
+        ),
         "_tclsh": attr.label(
             default = "@tcl_lang//:tclsh",
             executable = True,