diff --git a/usr.bin/elfctl/elfctl.c b/usr.bin/elfctl/elfctl.c
--- a/usr.bin/elfctl/elfctl.c
+++ b/usr.bin/elfctl/elfctl.c
@@ -51,7 +51,7 @@
 
 __FBSDID("$FreeBSD$");
 
-static bool convert_to_feature_val(char *, uint32_t *);
+static bool convert_to_feature_val(const char *, uint32_t *);
 static bool edit_file_features(Elf *, int, int, char *, bool);
 static bool get_file_features(Elf *, int, int, uint32_t *, uint64_t *, bool);
 static void print_features(void);
@@ -222,9 +222,9 @@
 }
 
 static bool
-convert_to_feature_val(char *feature_str, uint32_t *feature_val)
+convert_to_feature_val(const char *feature_str, uint32_t *feature_val)
 {
-	char *feature;
+	char *feature, *feature_tmp;
 	int i, len;
 	uint32_t input;
 	char operation;
@@ -236,8 +236,10 @@
 	if (operation != '+' && operation != '-' && operation != '=')
 		errx(1, "'%c' not an operator - use '+', '-', '='", operation);
 
+	if ((feature_tmp = strdup(feature_str)) == NULL)
+		err(1, "strdup");
 	len = nitems(featurelist);
-	while ((feature = strsep(&feature_str, ",")) != NULL) {
+	while ((feature = strsep(&feature_tmp, ",")) != NULL) {
 		for (i = 0; i < len; ++i) {
 			if (strcmp(featurelist[i].alias, feature) == 0) {
 				input |= featurelist[i].value;
@@ -267,13 +269,16 @@
 					errno = ERANGE;
 				if (errno != 0) {
 					warn("%s invalid", feature);
+					free(feature_tmp);
 					return (false);
 				}
 				input |= val;
 			} else {
 				warnx("%s is not a valid feature", feature);
-				if (!iflag)
+				if (!iflag) {
+					free(feature_tmp);
 					return (false);
+				}
 			}
 		}
 	}
@@ -285,6 +290,7 @@
 	} else if (operation == '-') {
 		*feature_val &= ~input;
 	}
+	free(feature_tmp);
 	return (true);
 }