Index: lib/Sema/SemaInit.cpp
===================================================================
--- lib/Sema/SemaInit.cpp
+++ lib/Sema/SemaInit.cpp
@@ -4877,6 +4877,13 @@
     return;
   }
 
+  // As an extension, and to fix Core issue 1013, zero initialize nullptr_t.
+  // Since there is only 1 valid value of nullptr_t, we can just use that.
+  if (DestType->isNullPtrType()) {
+    Sequence.AddZeroInitializationStep(Entity.getType());
+    return;
+  }
+
   //     - otherwise, no initialization is performed.
 
   //   If a program calls for the default initialization of an object of
Index: test/SemaCXX/nullptr_t-init.cpp
===================================================================
--- /dev/null
+++ test/SemaCXX/nullptr_t-init.cpp
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -ffreestanding -Wuninitialized %s
+// expected-no-diagnostics
+typedef decltype(nullptr) nullptr_t;
+
+// Ensure no 'uninitialized when used here' warnings (Wuninitialized), for 
+// nullptr_t always-initialized extension.
+nullptr_t default_init() {
+  nullptr_t a;
+  return a;
+}