diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index ac46180..ccd3762 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -1133,9 +1133,14 @@
 /// getConstantArrayType - Return the unique reference to the type for an 
 /// array of the specified element type.
 QualType ASTContext::getConstantArrayType(QualType EltTy, 
-                                          const llvm::APInt &ArySize,
+                                          const llvm::APInt &ArySizeIn,
                                           ArrayType::ArraySizeModifier ASM,
                                           unsigned EltTypeQuals) {
+  // Convert the array size into a canonical width matching the pointer size for
+  // the target.
+  llvm::APInt ArySize(ArySizeIn);
+  ArySize.zextOrTrunc(Target.getPointerWidth(EltTy.getAddressSpace()));
+  
   llvm::FoldingSetNodeID ID;
   ConstantArrayType::Profile(ID, EltTy, ArySize, ASM, EltTypeQuals);
       
diff --git a/test/Sema/types.c b/test/Sema/types.c
index 3ee7675..7ab4e06 100644
--- a/test/Sema/types.c
+++ b/test/Sema/types.c
@@ -19,3 +19,14 @@
   int __int128_t;
   int __uint128_t;
 }
+
+
+// Array type merging should convert array size to whatever matches the target
+// pointer size.
+// rdar://6880874
+extern int i[1LL];
+int i[(short)1];
+
+enum e { e_1 };
+extern int j[sizeof(enum e)];  // expected-note {{previous definition}}
+int j[42];   // expected-error {{redefinition of 'j' with a different type}}