diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5799,6 +5799,8 @@
   InGroup<MicrosoftRedeclareStatic>;
 def err_non_static_static : Error<
   "non-static declaration of %0 follows static declaration">;
+def err_extern_static : Error<
+  "extern declaration of %0 follows static declaration">;
 def err_extern_non_extern : Error<
   "extern declaration of %0 follows non-extern declaration">;
 def err_non_extern_extern : Error<
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
@@ -4637,6 +4637,15 @@
   //   the prior declaration. If no prior declaration is visible, or
   //   if the prior declaration specifies no linkage, then the
   //   identifier has external linkage.
+
+  if (New->hasExternalStorage() &&
+      Old->getCanonicalDecl()->getStorageClass() == SC_Static &&
+      Old->isLocalVarDeclOrParm()) {
+    Diag(New->getLocation(), diag::err_extern_static) << New->getDeclName();
+    Diag(OldLocation, PrevDiag);
+    return New->setInvalidDecl();
+  }
+
   if (New->hasExternalStorage() && Old->hasLinkage())
     /* Okay */;
   else if (New->getCanonicalDecl()->getStorageClass() != SC_Static &&
diff --git a/clang/test/SemaCXX/extern_static.cpp b/clang/test/SemaCXX/extern_static.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/SemaCXX/extern_static.cpp
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+void f(void)
+{
+    static int x; // expected-note {{previous definition is here}}
+    extern int x; // expected-error {{extern declaration of 'x' follows static declaration}}
+}
\ No newline at end of file