diff --git a/lib/ExecutionEngine/JIT/JIT.cpp b/lib/ExecutionEngine/JIT/JIT.cpp
index 57ae15e7fe9..766d62ce194 100644
--- a/lib/ExecutionEngine/JIT/JIT.cpp
+++ b/lib/ExecutionEngine/JIT/JIT.cpp
@@ -238,9 +238,9 @@ GenericValue JIT::runFunction(Function *F,
 ///
 void JIT::runJITOnFunction(Function *F) {
   static bool isAlreadyCodeGenerating = false;
-  assert(!isAlreadyCodeGenerating && "Error: Recursive compilation detected!");
 
   MutexGuard locked(lock);
+  assert(!isAlreadyCodeGenerating && "Error: Recursive compilation detected!");
 
   // JIT the function
   isAlreadyCodeGenerating = true;