2 files changed, 6 insertions, 1 deletions

diff --git a/src/io/cli.c b/src/io/cli.c
index 2ca4b29..14d51f8 100644
--- a/src/io/cli.c
+++ b/src/io/cli.c
@@ -380,7 +380,11 @@ error_t cli_parse(int key, char *arg, struct argp_state *state) {
 				argp_usage(state);
 			}
 
-			cfg->bits = strtoul(arg, NULL, 10);
+			char *bits_end = NULL;
+			cfg->bits = strtoul(arg, &bits_end, 10);
+			if (*bits_end != '\0') {
+				argp_failure(state, 1, 0, "Invalid bit size specified.");
+			}
 			cfg->hex_digits =
 			    2 * (cfg->bits / 8 + (cfg->bits % 8 != 0 ? 1 : 0));
 			break;
diff --git a/test/ecgen.sh b/test/ecgen.sh
index c8f1d96..2378abd 100755
--- a/test/ecgen.sh
+++ b/test/ecgen.sh
@@ -129,6 +129,7 @@ function cli() {
 	assert_raises "${ecgen} --brainpool-rfc=01234 --fp 10" 1
 	assert_raises "${ecgen} --ansi=01234 --fp 10" 1
 	assert_raises "${ecgen} --hex-check=not_hex --fp 10" 1
+	assert_raises "${ecgen} abc" 1
 }
 
 function hex() {