diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index a43cf5dc3448..9aae77090a5a 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1378,6 +1378,8 @@ def err_alignof_incomplete_type : Error<
   "invalid application of '__alignof' to an incomplete type %0">;
 def err_sizeof_alignof_bitfield : Error<
   "invalid application of '%select{sizeof|__alignof}0' to bit-field">;
+def err_offsetof_incomplete_type : Error<
+  "offsetof of incomplete type %0">;
 def err_offsetof_record_type : Error<
   "offsetof requires struct, union, or class type, %0 invalid">;
 def err_offsetof_array_type : Error<"offsetof requires array type, %0 invalid">;
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index f1014c6dfecc..2c54a792c1ae 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -5707,6 +5707,10 @@ Sema::OwningExprResult Sema::ActOnBuiltinOffsetOf(Scope *S,
   if (!Dependent) {
     bool DidWarnAboutNonPOD = false;
 
+    if (RequireCompleteType(TypeLoc, Res->getType(),
+                            diag::err_offsetof_incomplete_type))
+      return ExprError();
+
     // FIXME: Dependent case loses a lot of information here. And probably
     // leaks like a sieve.
     for (unsigned i = 0; i != NumComponents; ++i) {
diff --git a/clang/test/Sema/offsetof.c b/clang/test/Sema/offsetof.c
index f8b9fed03c3c..dfae99216f8a 100644
--- a/clang/test/Sema/offsetof.c
+++ b/clang/test/Sema/offsetof.c
@@ -48,3 +48,9 @@ int a[__builtin_offsetof(struct sockaddr_un, sun_path[len+1])];
 // PR4079
 union x {struct {int x;};};
 int x[__builtin_offsetof(union x, x)];
+
+// rdar://problem/7222956
+struct incomplete; // expected-note 2 {{forward declaration of 'struct incomplete'}}
+int test1[__builtin_offsetof(struct incomplete, foo)]; // expected-error {{offsetof of incomplete type 'struct incomplete'}}
+
+int test1[__builtin_offsetof(struct incomplete[10], [4].foo)]; // expected-error {{array has incomplete element type 'struct incomplete'}}