diff --git a/lib/IR/InlineAsm.cpp b/lib/IR/InlineAsm.cpp
index a3e1da3b189..16d874f32fc 100644
--- a/lib/IR/InlineAsm.cpp
+++ b/lib/IR/InlineAsm.cpp
@@ -91,6 +91,10 @@ bool InlineAsm::ConstraintInfo::Parse(StringRef Str,
   if (*I == '~') {
     Type = isClobber;
     ++I;
+
+    // '{' must immediately follow '~'.
+    if (I != E && *I != '{')
+      return true;
   } else if (*I == '=') {
     ++I;
     Type = isOutput;
diff --git a/test/Assembler/inline-asm-clobber.ll b/test/Assembler/inline-asm-clobber.ll
new file mode 100644
index 00000000000..65c8e444e80
--- /dev/null
+++ b/test/Assembler/inline-asm-clobber.ll
@@ -0,0 +1,10 @@
+; RUN: not llvm-as <%s 2>&1  | FileCheck %s
+
+; "~x{21}" is not a valid clobber constraint.
+
+; CHECK: invalid type for inline asm constraint string
+
+define void @foo() nounwind {
+  call void asm sideeffect "mov x0, #42", "~{x0},~{x19},~x{21}"() nounwind
+  ret void
+}