diff --git a/lib/Transforms/Scalar/ObjCARC.cpp b/lib/Transforms/Scalar/ObjCARC.cpp
index d753cf193fb..f978f571c6c 100644
--- a/lib/Transforms/Scalar/ObjCARC.cpp
+++ b/lib/Transforms/Scalar/ObjCARC.cpp
@@ -746,7 +746,6 @@ ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) {
   switch (GetBasicInstructionClass(CS.getInstruction())) {
   case IC_Retain:
   case IC_RetainRV:
-  case IC_RetainBlock:
   case IC_Autorelease:
   case IC_AutoreleaseRV:
   case IC_NoopCast:
@@ -754,6 +753,8 @@ ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) {
   case IC_FusedRetainAutorelease:
   case IC_FusedRetainAutoreleaseRV:
     // These functions don't access any memory visible to the compiler.
+    // Note that this doesn't include objc_retainBlock, becuase it updates
+    // pointers when it copies block data.
     return NoModRef;
   default:
     break;
diff --git a/test/Transforms/ObjCARC/retain-block-side-effects.ll b/test/Transforms/ObjCARC/retain-block-side-effects.ll
new file mode 100644
index 00000000000..e84d48f8691
--- /dev/null
+++ b/test/Transforms/ObjCARC/retain-block-side-effects.ll
@@ -0,0 +1,39 @@
+; RUN: opt -S -objc-arc-aa -basicaa -gvn < %s | FileCheck %s
+; rdar://10050579
+
+; objc_retainBlock stores into %repeater so the load from after the
+; call isn't forwardable from the store before the call.
+
+; CHECK: %tmp16 = call i8* @objc_retainBlock(i8* %tmp15) nounwind
+; CHECK: %tmp17 = bitcast i8* %tmp16 to void ()*
+; CHECK: %tmp18 = load %struct.__block_byref_repeater** %byref.forwarding, align 8
+; CHECK: %repeater12 = getelementptr inbounds %struct.__block_byref_repeater* %tmp18, i64 0, i32 6
+; CHECK: store void ()* %tmp17, void ()** %repeater12, align 8
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+
+%0 = type opaque
+%struct.__block_byref_repeater = type { i8*, %struct.__block_byref_repeater*, i32, i32, i8*, i8*, void ()* }
+%struct.__block_descriptor = type { i64, i64 }
+
+define void @foo() noreturn {
+entry:
+  %repeater = alloca %struct.__block_byref_repeater, align 8
+  %block = alloca <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, %0*, i8* }>, align 8
+  %byref.forwarding = getelementptr inbounds %struct.__block_byref_repeater* %repeater, i64 0, i32 1
+  %tmp10 = getelementptr inbounds %struct.__block_byref_repeater* %repeater, i64 0, i32 6
+  store void ()* null, void ()** %tmp10, align 8
+  %block.captured11 = getelementptr inbounds <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, %0*, i8* }>* %block, i64 0, i32 6
+  %tmp14 = bitcast %struct.__block_byref_repeater* %repeater to i8*
+  store i8* %tmp14, i8** %block.captured11, align 8
+  %tmp15 = bitcast <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, %0*, i8* }>* %block to i8*
+  %tmp16 = call i8* @objc_retainBlock(i8* %tmp15) nounwind
+  %tmp17 = bitcast i8* %tmp16 to void ()*
+  %tmp18 = load %struct.__block_byref_repeater** %byref.forwarding, align 8
+  %repeater12 = getelementptr inbounds %struct.__block_byref_repeater* %tmp18, i64 0, i32 6
+  %tmp13 = load void ()** %repeater12, align 8
+  store void ()* %tmp17, void ()** %repeater12, align 8
+  ret void
+}
+
+declare i8* @objc_retainBlock(i8*)