diff --git a/magik-squid/src/main/java/nl/ramsolutions/sw/magik/analysis/typing/types/TypeString.java b/magik-squid/src/main/java/nl/ramsolutions/sw/magik/analysis/typing/types/TypeString.java
index a988c4af..f0dca2b8 100644
--- a/magik-squid/src/main/java/nl/ramsolutions/sw/magik/analysis/typing/types/TypeString.java
+++ b/magik-squid/src/main/java/nl/ramsolutions/sw/magik/analysis/typing/types/TypeString.java
@@ -177,11 +177,28 @@ public String getFullString() {
         return this.currentPackage + ":" + this.string;
     }
 
+    /**
+     * Test if this type is undefined.
+     * @return {@code true} if this type is undefined.
+     */
     public boolean isUndefined() {
         return !this.isCombined()
             && this.getString().equalsIgnoreCase(UndefinedType.SERIALIZED_NAME);
     }
 
+    /**
+     * Test if this type contains an undefined type.
+     * @return {@code true} if this type contains an undefined type.
+     */
+    public boolean containsUndefined() {
+        if (this.isCombined()) {
+            return this.combinedTypes.stream()
+                .anyMatch(TypeString::containsUndefined);
+        }
+
+        return this.isUndefined();
+    }
+
     public boolean isSelf() {
         return !this.isCombined()
             && this.getString().equalsIgnoreCase(SelfType.SERIALIZED_NAME);
diff --git a/magik-typed-checks/src/main/java/nl/ramsolutions/sw/magik/typedchecks/fixers/TypeDocReturnTypeFixer.java b/magik-typed-checks/src/main/java/nl/ramsolutions/sw/magik/typedchecks/fixers/TypeDocReturnTypeFixer.java
index 48c4fa95..6a0c9df5 100644
--- a/magik-typed-checks/src/main/java/nl/ramsolutions/sw/magik/typedchecks/fixers/TypeDocReturnTypeFixer.java
+++ b/magik-typed-checks/src/main/java/nl/ramsolutions/sw/magik/typedchecks/fixers/TypeDocReturnTypeFixer.java
@@ -63,27 +63,26 @@ private List<CodeAction> extractReturnTypeCodeActions(
         return StreamUtils.zip(methodResultString.stream(), typeDocNodes.entrySet().stream())
             .map(entry -> {
                 final TypeString methodTypeString = entry.getKey();
-                if (methodTypeString == TypeString.UNDEFINED) {
+                if (methodTypeString != null && methodTypeString.containsUndefined()) {
                     // Don't propose code actions for undefined types.
                     return null;
                 }
 
                 final Map.Entry<AstNode, TypeString> typeDocEntry = entry.getValue();
                 if (methodTypeString != null && typeDocEntry == null) {
-                    // Code action: Add type-doc line.
                     return this.createAddReturnCodeAction(methodDefinition, methodTypeString);
                 }
 
-                final TypeString typeDocTypeString = typeDocEntry.getValue();
                 final AstNode typeDocNode = typeDocEntry.getKey();
                 final AstNode typeValueNode = typeDocNode.getFirstChild(TypeDocGrammar.TYPE_VALUE);
                 if (methodTypeString == null && typeDocEntry != null) {
-                    // Code action: Remove type-doc line.
                     return this.createRemoveReturnCodeAction(typeValueNode);
-                } else if (methodTypeString != null  // && typeDocTypeString != null
-                    && methodTypeString != TypeString.UNDEFINED
+                }
+
+                final TypeString typeDocTypeString = typeDocEntry.getValue();
+                if (methodTypeString != null  // && typeDocTypeString != null
+                    && !methodTypeString.containsUndefined()
                     && !methodTypeString.equals(typeDocTypeString)) {
-                    // Code action: Update type-doc line.
                     return this.createUpdateReturnCodeAction(methodTypeString, typeValueNode);
                 }