diff --git a/lib/System/ThreadLocal.cpp b/lib/System/ThreadLocal.cpp
index 8d119fb..74afa3e 100644
--- a/lib/System/ThreadLocal.cpp
+++ b/lib/System/ThreadLocal.cpp
@@ -49,7 +49,7 @@
 ThreadLocalImpl::~ThreadLocalImpl() {
   pthread_key_t* key = static_cast<pthread_key_t*>(data);
   int errorcode = pthread_key_delete(*key);
-  assert(errorcode = 0);
+  assert(errorcode == 0);
   delete key;
 }