diff --git a/tools/flock/src/flock.c b/tools/flock/src/flock.c
index 13baec4..02f7f60 100644
--- a/tools/flock/src/flock.c
+++ b/tools/flock/src/flock.c
@@ -205,11 +205,11 @@ int main(int argc, char *argv[])
     }
 
     filename = argv[optind];
-    fd = open(filename, O_RDONLY|O_NOCTTY|O_CREAT, 0666);
+    fd = open(filename, O_RDWR|O_NOCTTY|O_CREAT, 0666);
     /* Linux doesn't like O_CREAT on a directory, even though it should be a
        no-op */
     if (fd < 0 && errno == EISDIR)
-        fd = open(filename, O_RDONLY|O_NOCTTY);
+        fd = open(filename, O_RDWR|O_NOCTTY);
 
     if ( fd < 0 ) {
       err = errno;