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 2e0ba985b97..94f8aa1a713 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
@@ -8477,4 +8477,17 @@ public class AST2TemplateTests extends AST2TestBase {
 	public void testConstexprFunctionCallWithNonConstexprArguments_429891() throws Exception {
 		parseAndCheckBindings();
 	}
+	
+	//	constexpr int naive_fibonacci(int x) {
+	//		return x == 0 ? 0
+	//			 : x == 1 ? 1
+	//			 : naive_fibonacci(x - 2) + naive_fibonacci(x - 1);
+	//	}
+	//
+	//	constexpr int waldo = naive_fibonacci(5);
+	public void testConditionalExpressionFolding_429891() throws Exception {
+		BindingAssertionHelper helper = getAssertionHelper();
+		IVariable waldo = helper.assertNonProblem("waldo");
+		assertEquals(5, waldo.getInitialValue().numericalValue().longValue());
+	}
 }
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/EvalConditional.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/EvalConditional.java
index 9216b7ef7fd..822ea150963 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/EvalConditional.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/EvalConditional.java
@@ -356,6 +356,18 @@ public class EvalConditional extends CPPDependentEvaluation {
 	public ICPPEvaluation computeForFunctionCall(CPPFunctionParameterMap parameterMap,
 			int maxdepth, IASTNode point) {
 		ICPPEvaluation condition = fCondition.computeForFunctionCall(parameterMap, maxdepth, point);
+		// If the condition can be evaluated, fold the conditional into
+		// just the branch that is taken. This avoids infinite recursion
+		// when computing a recursive constexpr function where the base
+		// case of the recursion is one of the branches of the conditional.
+		Long conditionValue = condition.getValue(point).numericalValue();
+		if (conditionValue != null) {
+			if (conditionValue.longValue() != 0) {
+				return fPositive == null ? null : fPositive.computeForFunctionCall(parameterMap, maxdepth, point);
+			} else {
+				return fNegative.computeForFunctionCall(parameterMap, maxdepth, point);
+			}
+		}
 		ICPPEvaluation positive = fPositive == null ?
 				null : fPositive.computeForFunctionCall(parameterMap, maxdepth, point);
 		ICPPEvaluation negative = fNegative.computeForFunctionCall(parameterMap, maxdepth, point);