diff --git a/src/x64/regexp-macro-assembler-x64.cc b/src/x64/regexp-macro-assembler-x64.cc
index 383399ea60..fcb5aa5aa6 100644
--- a/src/x64/regexp-macro-assembler-x64.cc
+++ b/src/x64/regexp-macro-assembler-x64.cc
@@ -1245,17 +1245,38 @@ void RegExpMacroAssemblerX64::BranchOrBacktrack(Condition condition,
 
 void RegExpMacroAssemblerX64::SafeCall(Label* to) {
   __ call(to);
+//// TESTING CODE - REVERT WHEN TEST IS DONE.
+  __ nop();
+//// END TESTING CODE
 }
 
 
 void RegExpMacroAssemblerX64::SafeCallTarget(Label* label) {
   __ bind(label);
+  //// TESTING CODE - REVERT WHEN TEST IS DONE.
+    __ movq(rax, Operand(rsp, 0));
+    __ movb(rax, Operand(rax, 0));
+    __ cmpb(rax, Immediate(0x90));  // Points to nop.
+    Label ok;
+    __ j(equal, &ok);
+    __ int3();
+    __ bind(&ok);
+  //// END TESTING CODE
   __ subq(Operand(rsp, 0), code_object_pointer());
 }
 
 
 void RegExpMacroAssemblerX64::SafeReturn() {
   __ addq(Operand(rsp, 0), code_object_pointer());
+//// TESTING CODE - REVERT WHEN TEST IS DONE.
+  __ movq(rax, Operand(rsp, 0));
+  __ movb(rax, Operand(rax, 0));
+  __ cmpb(rax, Immediate(0x90));  // Points to nop.
+  Label ok;
+  __ j(equal, &ok);
+  __ int3();
+  __ bind(&ok);
+//// END TESTING CODE
   __ ret(0);
 }