diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index 27e13e4..9d05769 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -103,7 +103,7 @@
 /*
  * Prototypes
  */
-#if __cplusplus
+#ifdef __cplusplus
 extern "C" {
 #endif
 
@@ -302,7 +302,7 @@
         __pthread_cleanup_pop( &__cleanup, (execute)); \
     } while (0);
 
-#if __cplusplus
+#ifdef __cplusplus
 } /* extern "C" */
 #endif