diff -up shadow-4.9/man/usermod.8.xml.badname-special-characters shadow-4.9/man/usermod.8.xml
--- shadow-4.9/man/usermod.8.xml.badname-special-characters	2021-07-22 23:55:35.000000000 +0200
+++ shadow-4.9/man/usermod.8.xml	2022-09-26 16:32:46.214519257 +0200
@@ -110,7 +110,7 @@
       </varlistentry>
       <varlistentry>
 	<term>
-	  <option>-b</option>, <option>--badnames</option>
+	  <option>-b</option>, <option>--badname</option>
 	</term>
 	<listitem>
 	  <para>
diff -up shadow-4.9/src/newusers.c.badname-special-characters shadow-4.9/src/newusers.c
--- shadow-4.9/src/newusers.c.badname-special-characters	2021-07-22 23:55:35.000000000 +0200
+++ shadow-4.9/src/newusers.c	2022-09-26 16:33:31.331869855 +0200
@@ -139,7 +139,7 @@ static void usage (int status)
 	                  "\n"
 	                  "Options:\n"),
 	                Prog);
-	(void) fputs (_("  -b, --badnames                allow bad names\n"), usageout);
+	(void) fputs (_("  -b, --badname                 allow bad names\n"), usageout);
 #ifndef USE_PAM
 	(void) fprintf (usageout,
 	                _("  -c, --crypt-method METHOD     the crypt method (one of %s)\n"),
@@ -406,7 +406,7 @@ static int add_user (const char *name, u
 	/* Check if this is a valid user name */
 	if (!is_valid_user_name (name)) {
 		fprintf (stderr,
-		         _("%s: invalid user name '%s'\n"),
+		         _("%s: invalid user name '%s': use --badname to ignore\n"),
 		         Prog, name);
 		return -1;
 	}
@@ -634,7 +634,7 @@ static void process_flags (int argc, cha
         int bad_s;
 #endif				/* USE_SHA_CRYPT || USE_BCRYPT || USE_YESCRYPT */
 	static struct option long_options[] = {
-		{"badnames",     no_argument,       NULL, 'b'},
+		{"badname",      no_argument,       NULL, 'b'},
 #ifndef USE_PAM
 		{"crypt-method", required_argument, NULL, 'c'},
 #endif				/* !USE_PAM */
diff -up shadow-4.9/src/pwck.c.badname-special-characters shadow-4.9/src/pwck.c
--- shadow-4.9/src/pwck.c.badname-special-characters	2022-09-26 16:32:46.208519211 +0200
+++ shadow-4.9/src/pwck.c	2022-09-26 16:32:46.214519257 +0200
@@ -151,7 +151,7 @@ static /*@noreturn@*/void usage (int sta
 		                  "Options:\n"),
 		                Prog);
 	}
-	(void) fputs (_("  -b, --badnames                allow bad names\n"), usageout);
+	(void) fputs (_("  -b, --badname                 allow bad names\n"), usageout);
 	(void) fputs (_("  -h, --help                    display this help message and exit\n"), usageout);
 	(void) fputs (_("  -q, --quiet                   report errors only\n"), usageout);
 	(void) fputs (_("  -r, --read-only               display errors and warnings\n"
@@ -176,7 +176,7 @@ static void process_flags (int argc, cha
 {
 	int c;
 	static struct option long_options[] = {
-		{"badnames",  no_argument,       NULL, 'b'},
+		{"badname",   no_argument,       NULL, 'b'},
 		{"help",      no_argument,       NULL, 'h'},
 		{"quiet",     no_argument,       NULL, 'q'},
 		{"read-only", no_argument,       NULL, 'r'},
@@ -493,7 +493,8 @@ static void check_pw_file (int *errors,
 		 */
 
 		if (!is_valid_user_name (pwd->pw_name)) {
-			printf (_("invalid user name '%s'\n"), pwd->pw_name);
+			printf (_("invalid user name '%s': use --badname to ignore\n"),
+					pwd->pw_name);
 			*errors += 1;
 		}
 
diff -up shadow-4.9/src/useradd.c.badname-special-characters shadow-4.9/src/useradd.c
--- shadow-4.9/src/useradd.c.badname-special-characters	2022-09-26 16:32:46.212519242 +0200
+++ shadow-4.9/src/useradd.c	2022-09-26 16:32:46.214519257 +0200
@@ -852,7 +852,7 @@ static void usage (int status)
 	                  "\n"
 	                  "Options:\n"),
 	                Prog, Prog, Prog);
-	(void) fputs (_("      --badnames                do not check for bad names\n"), usageout);
+	(void) fputs (_("      --badname                 do not check for bad names\n"), usageout);
 	(void) fputs (_("  -b, --base-dir BASE_DIR       base directory for the home directory of the\n"
 	                "                                new account\n"), usageout);
 #ifdef WITH_BTRFS
@@ -1119,7 +1119,7 @@ static void process_flags (int argc, cha
 #ifdef WITH_BTRFS
 			{"btrfs-subvolume-home", no_argument, NULL, 200},
 #endif
-			{"badnames",       no_argument,       NULL, 201},
+			{"badname",        no_argument,       NULL, 201},
 			{"comment",        required_argument, NULL, 'c'},
 			{"home-dir",       required_argument, NULL, 'd'},
 			{"defaults",       no_argument,       NULL, 'D'},
diff -up shadow-4.9/src/usermod.c.badname-special-characters shadow-4.9/src/usermod.c
--- shadow-4.9/src/usermod.c.badname-special-characters	2022-09-26 16:32:46.215519265 +0200
+++ shadow-4.9/src/usermod.c	2022-09-26 16:33:52.274032599 +0200
@@ -418,7 +418,7 @@ static /*@noreturn@*/void usage (int sta
 	                  "\n"
 	                  "Options:\n"),
 	                Prog);
-	(void) fputs (_("  -b, --badnames                allow bad names\n"), usageout);
+	(void) fputs (_("  -b, --badname                 allow bad names\n"), usageout);
 	(void) fputs (_("  -c, --comment COMMENT         new value of the GECOS field\n"), usageout);
 	(void) fputs (_("  -d, --home HOME_DIR           new home directory for the user account\n"), usageout);
 	(void) fputs (_("  -e, --expiredate EXPIRE_DATE  set account expiration date to EXPIRE_DATE\n"), usageout);