diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -9195,6 +9195,7 @@
             << Name << RemoveRange
             << FixItHint::CreateRemoval(RemoveRange)
             << FixItHint::CreateInsertion(InsertLoc, "<>");
+          Invalid = true;
         }
       }
     } else {
diff --git a/clang/test/CXX/temp/temp.spec/temp.expl.spec/p20-2.cpp b/clang/test/CXX/temp/temp.spec/temp.expl.spec/p20-2.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/CXX/temp/temp.spec/temp.expl.spec/p20-2.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+template<typename T>
+void f(T);
+
+template<typename T>
+struct A {
+  // expected-error@+1{{cannot declare an explicit specialization in a friend}}
+  template <> friend void f<>(int) {}
+};
+
+// Makes sure implicit instantiation here does not trigger
+// the assertion "Member specialization must be an explicit specialization"
+void foo(void) {
+    A<int> a;
+}
\ No newline at end of file