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 b3c094d144f..15aa882b93a 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
@@ -9463,6 +9463,14 @@ public class AST2TemplateTests extends AST2TestBase {
 		parseAndCheckBindings();
 	}
 
+	//	template <int I, typename T>
+	//	constexpr int waldo(T v) {
+	//	  return v < I ? 1 : 1 + waldo<I, T>(v / I);
+	//	}
+	public void _testAmbiguityResolution_497931() throws Exception {
+		parseAndCheckBindings();
+	}
+
 	//	template <typename> struct S {};
 	//	struct U {};
 	//
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/TemplateIdStrategy.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/TemplateIdStrategy.java
index 28eaeb970c5..2fdf91f996d 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/TemplateIdStrategy.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/TemplateIdStrategy.java
@@ -118,8 +118,9 @@ final class TemplateIdStrategy implements ITemplateIdStrategy {
 				// Optimization (bug 363609): if during the previous alternative, a name was parsed as a
 				// template-id with multiple template arguments, it's not going to be parsed differently in
 				// a subsequent alternative, so keep it as a template-id.
-				// Of course, this optimization is only sound if the previous alternative was parsed
+				// Of course, this optimization is only possible if the previous alternative was parsed
 				// successfully (bug 445177).
+				// TODO: This optimization is invalid since it triggers bug 497931.
 				if (previousAlternativeFailedToParse || nameLen == 0 || !hasMultipleArgs(names[--nameLen])) {
 					fSimpleIDs.clear(bp+1, Integer.MAX_VALUE);
 					fSimpleIDs.set(bp);