diff --git a/dlls/mountmgr.sys/device.c b/dlls/mountmgr.sys/device.c
index 005ec5ec64a..028c17f9a3d 100644
--- a/dlls/mountmgr.sys/device.c
+++ b/dlls/mountmgr.sys/device.c
@@ -534,7 +534,7 @@ static void set_drive_info( struct dos_drive *drive, int letter, struct volume *
     }
 }
 
-static inline int is_valid_device( struct stat *st )
+static inline BOOL is_valid_device( struct stat *st )
 {
 #if defined(linux) || defined(__sun__)
     return S_ISBLK( st->st_mode );