diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index f9a462b..9e7e94f 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1621,6 +1621,9 @@
   "invalid conversion '%0'">, InGroup<Format>;
 def warn_printf_missing_format_string : Warning<
   "format string missing">, InGroup<Format>;
+def warn_null_arg : Warning<
+  "argument is null where non-null is required">,
+  InGroup<DiagGroup<"nonnull">>, DefaultIgnore;
 def warn_printf_empty_format_string : Warning<
   "format string is empty">, InGroup<FormatZeroLength>;
 def warn_printf_format_string_is_wide_literal : Warning<
diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index 9c294e0..2528431 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -2741,6 +2741,8 @@
   void CheckPrintfString(const StringLiteral *FExpr, const Expr *OrigFormatExpr,
                          const CallExpr *TheCall, bool HasVAListArg,
                          unsigned format_idx, unsigned firstDataArg);
+  void CheckNonNullArguments(const NonNullAttr *NonNull, 
+                             const CallExpr *TheCall);
   void CheckPrintfArguments(const CallExpr *TheCall, bool HasVAListArg, 
                             unsigned format_idx, unsigned firstDataArg);
   void CheckReturnStackAddr(Expr *RetValExp, QualType lhsType,
diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index e9ddce3..5a6babb 100644
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -178,6 +178,10 @@
                            HasVAListArg ? 0 : Format->getFirstArg() - 1);
     }
   }
+  for (const Attr *attr = FDecl->getAttrs(); attr; attr = attr->getNext()) {
+    if (const NonNullAttr *NonNull = dyn_cast<NonNullAttr>(attr))
+      CheckNonNullArguments(NonNull, TheCall);
+  }
 
   return move(TheCallResult);
 }
@@ -784,6 +788,16 @@
   }
 }
 
+void
+Sema::CheckNonNullArguments(const NonNullAttr *NonNull, const CallExpr *TheCall)
+{
+  for (NonNullAttr::iterator i = NonNull->begin(), e = NonNull->end();
+       i != e; ++i) {
+    const Expr *ArgExpr = TheCall->getArg(*i)->IgnoreParenCasts();
+    if (ArgExpr->isNullPointerConstant(Context))
+      Diag(ArgExpr->getLocStart(), diag::warn_null_arg);
+  }
+}
 
 /// CheckPrintfArguments - Check calls to printf (and similar functions) for
 /// correct use of format strings.  
diff --git a/test/Sema/nonnull-check.c b/test/Sema/nonnull-check.c
new file mode 100644
index 0000000..2d2a9f4
--- /dev/null
+++ b/test/Sema/nonnull-check.c
@@ -0,0 +1,26 @@
+// RUN: clang-cc -Wnonnull -fsyntax-only -verify %s
+
+extern void func1 (void (^block1)(), void (^block2)(), int) __attribute__((nonnull));
+
+extern void func3 (void (^block1)(), int, void (^block2)(), int)
+  __attribute__((nonnull(1,3)));
+
+extern void func4 (void (^block1)(), void (^block2)()) __attribute__((nonnull(1)))
+  __attribute__((nonnull(2)));
+
+void
+foo (int i1, int i2, int i3, void (^cp1)(), void (^cp2)(), void (^cp3)())
+{
+  func1(cp1, cp2, i1);
+
+  func1(0, cp2, i1);  // expected-warning {{argument is null where non-null is required}}
+  func1(cp1, 0, i1);  // expected-warning {{argument is null where non-null is required}}
+  func1(cp1, cp2, 0);
+
+
+  func3(0, i2, cp3, i3); // expected-warning {{argument is null where non-null is required}}
+  func3(cp3, i2, 0, i3);  // expected-warning {{argument is null where non-null is required}}
+
+  func4(0, cp1); // expected-warning {{argument is null where non-null is required}}
+  func4(cp1, 0); // expected-warning {{argument is null where non-null is required}}
+}