diff --git a/libs/pbd/pthread_utils.cc b/libs/pbd/pthread_utils.cc
index 534b2bfc99..918176ed8e 100644
--- a/libs/pbd/pthread_utils.cc
+++ b/libs/pbd/pthread_utils.cc
@@ -255,7 +255,7 @@ static size_t pbd_stack_size ()
 #ifndef NDEBUG
     printf("TLS of parent thread: %zd Bytes (pthread min-stack: %zu)\n", rv, pt_min_stack);
 #endif
-		assert (rc >= pt_min_stack);
+		assert (rv >= pt_min_stack);
 		rv -= pt_min_stack;
     pthread_attr_destroy(&attr);
   }