diff --git a/src/firejail/restrict_users.c b/src/firejail/restrict_users.c
index 741e908edc4..261c73ac586 100644
--- a/src/firejail/restrict_users.c
+++ b/src/firejail/restrict_users.c
@@ -212,7 +212,7 @@ static void sanitize_passwd(void) {
 		// process uid
 		int uid;
 		int rv = sscanf(ptr, "%d:", &uid);
-		if (rv == 0 || uid < 0)
+		if (rv != 1 || uid < 0)
 			goto errout;
 		assert(uid_min);
 		if (uid < uid_min || uid == 65534) { // on Debian platforms user nobody is 65534
@@ -351,7 +351,7 @@ static void sanitize_group(void) {
 		// process uid
 		int gid;
 		int rv = sscanf(ptr, "%d:", &gid);
-		if (rv == 0 || gid < 0)
+		if (rv != 1 || gid < 0)
 			goto errout;
 		assert(gid_min);
 		if (gid < gid_min || gid == 65534) { // on Debian platforms 65534 is group nogroup