diff --git a/VolumeManager.h b/VolumeManager.h
index 39fc8f9..dd9f09d 100644
--- a/VolumeManager.h
+++ b/VolumeManager.h
@@ -217,7 +217,7 @@
 
 extern "C" {
 #endif /* __cplusplus */
-#define UNMOUNT_NOT_MOUNTED_ERR -2
+#define UNMOUNT_NOT_MOUNTED_ERR (-2)
     int vold_unmountAll(void);
 #ifdef __cplusplus
 }