Index: include/clang/AST/TemplateBase.h
===================================================================
--- include/clang/AST/TemplateBase.h
+++ include/clang/AST/TemplateBase.h
@@ -465,7 +465,14 @@
 
   TemplateArgumentLoc(const TemplateArgument &Argument, Expr *E)
       : Argument(Argument), LocInfo(E) {
-    assert(Argument.getKind() == TemplateArgument::Expression);
+
+    /* When an error occurs in a template value that is defaulted to
+       nullptr then the nullptr is left as-is and this function will
+       take in an argument that is of type NullPtr when compiled using
+       C++17 standard.  This is to make sure the compiler does not crash
+       and proceeds through.  */
+    assert(Argument.getKind() == TemplateArgument::NullPtr ||
+           Argument.getKind() == TemplateArgument::Expression);
   }
 
   TemplateArgumentLoc(const TemplateArgument &Argument, 
Index: test/SemaObjCXX/class-templ-error-null-init.mm
===================================================================
--- /dev/null
+++ test/SemaObjCXX/class-templ-error-null-init.mm
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++17  -verify %s
+
+template <typename a, typename b, d * = nullptr> // expected-error {{unknown type name 'd'}}
+class e {
+  public:
+    e(a,b) {}
+};
+      e c([]{} ,[]{} );