diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2CPPTests.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2CPPTests.java
index 7d2815987cc..eb4b961ae3b 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2CPPTests.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2CPPTests.java
@@ -10125,6 +10125,21 @@ public class AST2CPPTests extends AST2TestBase {
 		parseAndCheckBindings(getAboveComment(), CPP, true);
 	}
 
+	//	template <typename T>
+	//	T bar();
+	//	struct S {
+	//	    void waldo();
+	//	};
+	//	int main() {
+	//	    auto L = [](S s) { return s; };
+	//	    typedef decltype(L) lambda_type;
+	//	    decltype(bar<const lambda_type>()(S())) v;
+	//	    v.waldo();
+	//	}
+	public void testDecltypeWithConstantLambda_397494() throws Exception {
+		parseAndCheckBindings();
+	}
+
 	//	template <bool>
 	//	struct enable_if {
 	//	};
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPClosureType.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPClosureType.java
index 14e1902fd42..979cc8fd7b3 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPClosureType.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPClosureType.java
@@ -103,7 +103,7 @@ public class CPPClosureType extends PlatformObject implements ICPPClassType, ICP
 		// Function call operator
 		final IType returnType= getReturnType();
 		final IType[] parameterTypes= getParameterTypes();
-		ft= new CPPFunctionType(returnType, parameterTypes, isMutable(), false, false);
+		ft= new CPPFunctionType(returnType, parameterTypes, !isMutable(), false, false);
 
 		ICPPParameter[] params = new ICPPParameter[parameterTypes.length];
 		for (int i = 0; i < params.length; i++) {