diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index abb98de..63e05f7 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -30,14 +30,14 @@ jobs:
         run: ./gradlew clean build
 
       - name: Archive test results
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         if: always() # run even if build failed
         with:
           name: test-results
           path: build/reports
 
       - name: Archive libs
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: libs
           path: build/libs
\ No newline at end of file
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 8f053e3..d5e6b65 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -65,7 +65,7 @@ jobs:
         run: ./gradlew jreleaserFullRelease
 
       - name: Archive artifacts
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: artifacts
           path: |
diff --git a/src/main/java/blue/language/merge/processor/DictionaryProcessor.java b/src/main/java/blue/language/merge/processor/DictionaryProcessor.java
index 58c1257..ee96f8a 100644
--- a/src/main/java/blue/language/merge/processor/DictionaryProcessor.java
+++ b/src/main/java/blue/language/merge/processor/DictionaryProcessor.java
@@ -15,7 +15,7 @@ public class DictionaryProcessor implements MergingProcessor {
 
     @Override
     public void process(Node target, Node source, NodeProvider nodeProvider, NodeResolver nodeResolver) {
-        if ((source.getKeyType() != null || source.getValueType() != null) && !Types.isDictionaryType(source.getType())) {
+        if ((source.getKeyType() != null || source.getValueType() != null) && !Types.isDictionaryType(source.getType(), nodeProvider)) {
             throw new IllegalArgumentException("Source node with keyType or valueType must have a Dictionary type");
         }
 
diff --git a/src/main/java/blue/language/merge/processor/ListProcessor.java b/src/main/java/blue/language/merge/processor/ListProcessor.java
index f8810c3..6336f61 100644
--- a/src/main/java/blue/language/merge/processor/ListProcessor.java
+++ b/src/main/java/blue/language/merge/processor/ListProcessor.java
@@ -14,7 +14,7 @@ public class ListProcessor implements MergingProcessor {
     @Override
     public void process(Node target, Node source, NodeProvider nodeProvider, NodeResolver nodeResolver) {
 
-        if (source.getItemType() != null && !Types.isListType(source.getType())) {
+        if (source.getItemType() != null && !Types.isListType(source.getType(), nodeProvider)) {
             throw new IllegalArgumentException("Source node with itemType must have a List type");
         }
 
diff --git a/src/main/java/blue/language/utils/Types.java b/src/main/java/blue/language/utils/Types.java
index 907a5cf..3dce885 100644
--- a/src/main/java/blue/language/utils/Types.java
+++ b/src/main/java/blue/language/utils/Types.java
@@ -113,12 +113,12 @@ public static boolean isBooleanType(Node typeNode, NodeProvider nodeProvider) {
     }
 
 
-    public static boolean isListType(Node typeNode) {
-        return typeNode.getBlueId() != null && LIST_TYPE_BLUE_ID.equals(typeNode.getBlueId());
+    public static boolean isListType(Node typeNode, NodeProvider nodeProvider) {
+        return isSubtype(typeNode, new Node().blueId(LIST_TYPE_BLUE_ID), nodeProvider);
     }
 
-    public static boolean isDictionaryType(Node typeNode) {
-        return typeNode.getBlueId() != null && DICTIONARY_TYPE_BLUE_ID.equals(typeNode.getBlueId());
+    public static boolean isDictionaryType(Node typeNode, NodeProvider nodeProvider) {
+        return isSubtype(typeNode, new Node().blueId(DICTIONARY_TYPE_BLUE_ID), nodeProvider);
     }
 
 }
\ No newline at end of file
diff --git a/src/test/java/blue/language/merge/MergerIntegrationTest.java b/src/test/java/blue/language/merge/MergerIntegrationTest.java
new file mode 100644
index 0000000..b44e925
--- /dev/null
+++ b/src/test/java/blue/language/merge/MergerIntegrationTest.java
@@ -0,0 +1,59 @@
+package blue.language.merge;
+
+import blue.language.Blue;
+import blue.language.model.Node;
+import blue.language.provider.BasicNodeProvider;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class MergerIntegrationTest {
+
+    private BasicNodeProvider nodeProvider;
+
+    @BeforeEach
+    public void setup() {
+        nodeProvider = new BasicNodeProvider();
+    }
+
+    @Test
+    public void shouldBeIdempotentWhenResolvingTheSameNodeTwice() {
+        nodeProvider.addSingleDocs(
+                "name: Document Anchor\n" +
+                "template:\n" +
+                "  description: Optional Blue document template.\n"
+        );
+
+        nodeProvider.addSingleDocs(
+                "name: Document Anchors\n" +
+                "type: Dictionary\n" +
+                "keyType: Text\n" +
+                "valueType:\n" +
+                "  blueId: " + nodeProvider.getBlueIdByName("Document Anchor") + "\n"
+        );
+
+        nodeProvider.addSingleDocs(
+                "name: My Entry\n" +
+                "type:\n" +
+                "  blueId: " + nodeProvider.getBlueIdByName("Document Anchors") + "\n" +
+                "anchor1:\n" +
+                "  type:\n" +
+                "    blueId: " + nodeProvider.getBlueIdByName("Document Anchor") + "\n" +
+                "anchor2:\n" +
+                "  type:\n" +
+                "    blueId: " + nodeProvider.getBlueIdByName("Document Anchor") + "\n"
+        );
+
+        Blue blue = new Blue(nodeProvider);
+
+        Node myEntry = nodeProvider.getNodeByName("My Entry");
+
+        Node resolvedNode = blue.resolve(myEntry);
+        Node resolvedNode2 = blue.resolve(resolvedNode);
+
+        assertEquals(blue.nodeToJson(resolvedNode), blue.nodeToJson(resolvedNode2));
+    }
+}
+
+