diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index 6f92f73..c3ecc2a 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -320,7 +320,8 @@ int os_file_size(char *file, unsigned long long *size_out)
 	}
 
 	if(S_ISBLK(buf.ust_mode)){
-		int fd, blocks;
+		int fd;
+		long blocks;
 
 		fd = os_open_file(file, of_read(OPENFLAGS()), 0);
 		if(fd < 0){