diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
index fb814126819..0028d9645d0 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
@@ -7310,6 +7310,17 @@ public class AST2TemplateTests extends AST2TestBase {
 		BindingAssertionHelper helper = new BindingAssertionHelper(getAboveComment(), true);
 		helper.assertProblem("bind(s, 0, foo)", "bind");
     }
+	
+
+	//	template<typename T>
+	//	T forward(T);
+	//	template <typename, typename S1, typename S2>
+	//	int combine(S1&& r1, S2&& r2);
+	//	template <typename S1, typename S2>
+	//	auto combine(S1 r1, S2 r2) -> decltype(combine<int>(forward<S1>(r1), forward<S2>(r2)));
+	public void testUnsupportedOperationExceptionInASTAmbiguousNode_402085() throws Exception {
+		parseAndCheckBindings();
+	}
 
 	//	template <bool... Args>
 	//	struct ice_or;
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPSemantics.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPSemantics.java
index 126a1dd02a6..1186983820e 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPSemantics.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPSemantics.java
@@ -699,6 +699,9 @@ public class CPPSemantics {
     private static void getAssociatedScopes(IType t, Set<ICPPNamespaceScope> namespaces,
     		Set<ICPPFunction> friendFns, ObjectSet<IType> handled, CPPASTTranslationUnit tu) throws DOMException {
         t = getNestedType(t, TDEF | CVTYPE | PTR | ARRAY | REF);
+        // No point getting namespaces associated with a dependent type - we don't know what they are yet.
+        if (CPPTemplates.isDependentType(t))
+        	return;
     	if (t instanceof IBinding) {
             if (handled.containsKey(t))
             	return;