diff --git a/include/newlib-freertos.h b/include/newlib-freertos.h
index 497ca52..a65e62e 100644
--- a/include/newlib-freertos.h
+++ b/include/newlib-freertos.h
@@ -52,7 +52,7 @@
 #endif
 
 #ifndef configSET_TLS_BLOCK
-    #define configSET_TLS_BLOCK( xTLSBlock )    _impure_ptr = &( xTLSBlock )
+    #define configSET_TLS_BLOCK( xTLSBlock )    ( _impure_ptr = &( xTLSBlock ) )
 #endif
 
 #ifndef configDEINIT_TLS_BLOCK