diff --git a/lib/CodeGen/Passes.cpp b/lib/CodeGen/Passes.cpp
index ec1f2b4c3b2..401ca657c40 100644
--- a/lib/CodeGen/Passes.cpp
+++ b/lib/CodeGen/Passes.cpp
@@ -69,7 +69,7 @@ static cl::opt<bool> DisableLSR("disable-lsr", cl::Hidden,
 static cl::opt<bool> DisableCGP("disable-cgp", cl::Hidden,
     cl::desc("Disable Codegen Prepare"));
 static cl::opt<bool> DisableCopyProp("disable-copyprop", cl::Hidden,
-    cl::desc("Disable Copy Propagation pass"));
+    cl::desc("Disable Copy Propagation pass"), cl::init(true)); // PR11940
 static cl::opt<bool> PrintLSR("print-lsr-output", cl::Hidden,
     cl::desc("Print LLVM IR produced by the loop-reduce pass"));
 static cl::opt<bool> PrintISelInput("print-isel-input", cl::Hidden,
diff --git a/test/CodeGen/X86/machine-cp.ll b/test/CodeGen/X86/machine-cp.ll
index 54fa01c38fd..772d2d080b6 100644
--- a/test/CodeGen/X86/machine-cp.ll
+++ b/test/CodeGen/X86/machine-cp.ll
@@ -1,4 +1,4 @@
-; RUN: llc -mtriple=x86_64-apple-macosx -mcpu=nocona < %s | FileCheck %s
+; RUN: llc -mtriple=x86_64-apple-macosx -mcpu=nocona < %s -disable-copyprop=false | FileCheck %s
 
 ; After tail duplication, two copies in an early exit BB can be cancelled out.
 ; rdar://10640363