Index: cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp
===================================================================
--- cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2110,6 +2110,8 @@
     Param->setInvalidDecl();
 
   if (D->hasDefaultArgument() && !D->defaultArgumentWasInherited()) {
+    EnterExpressionEvaluationContext ConstantEvaluated(SemaRef,
+                                                       Sema::ConstantEvaluated);
     ExprResult Value = SemaRef.SubstExpr(D->getDefaultArgument(), TemplateArgs);
     if (!Value.isInvalid())
       Param->setDefaultArgument(Value.get());
Index: cfe/trunk/test/SemaTemplate/default-arguments-cxx0x.cpp
===================================================================
--- cfe/trunk/test/SemaTemplate/default-arguments-cxx0x.cpp
+++ cfe/trunk/test/SemaTemplate/default-arguments-cxx0x.cpp
@@ -75,3 +75,13 @@
     g<int>();
   }
 }
+
+// rdar://problem/24480205
+namespace PR13986 {
+  constexpr unsigned Dynamic = 0;
+  template <unsigned> class A { template <unsigned = Dynamic> void m_fn1(); };
+  class Test {
+    ~Test() {}
+    A<1> m_target;
+  };
+}