diff --git a/src/util/efirom.c b/src/util/efirom.c
index 93cd79fe9..8fa15ca90 100644
--- a/src/util/efirom.c
+++ b/src/util/efirom.c
@@ -207,14 +207,14 @@ static int parse_options ( const int argc, char **argv,
 		switch ( c ) {
 		case 'v':
 			opts->vendor = strtoul ( optarg, &end, 16 );
-			if ( *end ) {
+			if ( *end || ( ! *optarg ) ) {
 				eprintf ( "Invalid vendor \"%s\"\n", optarg );
 				exit ( 2 );
 			}
 			break;
 		case 'd':
 			opts->device = strtoul ( optarg, &end, 16 );
-			if ( *end ) {
+			if ( *end || ( ! *optarg ) ) {
 				eprintf ( "Invalid device \"%s\"\n", optarg );
 				exit ( 2 );
 			}
diff --git a/src/util/elf2efi.c b/src/util/elf2efi.c
index bcd53c9af..4f517d7d2 100644
--- a/src/util/elf2efi.c
+++ b/src/util/elf2efi.c
@@ -996,7 +996,7 @@ static int parse_options ( const int argc, char **argv,
 		switch ( c ) {
 		case 's':
 			opts->subsystem = strtoul ( optarg, &end, 0 );
-			if ( *end ) {
+			if ( *end || ( ! *optarg ) ) {
 				eprintf ( "Invalid subsytem \"%s\"\n",
 					  optarg );
 				exit ( 2 );