diff --git a/cmd/zpool/zpool_main.c b/cmd/zpool/zpool_main.c
index 7a15c78d10..81bbf1375d 100644
--- a/cmd/zpool/zpool_main.c
+++ b/cmd/zpool/zpool_main.c
@@ -4965,8 +4965,8 @@ get_interval_count(int *argcp, char **argv, float *iv,
 
 		if (*end == '\0' && errno == 0) {
 			if (interval == 0) {
-				(void) fprintf(stderr, gettext("interval "
-				    "cannot be zero\n"));
+				(void) fprintf(stderr, gettext(
+				    "interval cannot be zero\n"));
 				usage(B_FALSE);
 			}
 			/*
@@ -4996,8 +4996,8 @@ get_interval_count(int *argcp, char **argv, float *iv,
 
 		if (*end == '\0' && errno == 0) {
 			if (interval == 0) {
-				(void) fprintf(stderr, gettext("interval "
-				    "cannot be zero\n"));
+				(void) fprintf(stderr, gettext(
+				    "interval cannot be zero\n"));
 				usage(B_FALSE);
 			}
 
diff --git a/lib/libzutil/zutil_nicenum.c b/lib/libzutil/zutil_nicenum.c
index 306cec3cad..1a19db0dfe 100644
--- a/lib/libzutil/zutil_nicenum.c
+++ b/lib/libzutil/zutil_nicenum.c
@@ -35,6 +35,9 @@
 boolean_t
 zfs_isnumber(const char *str)
 {
+	if (!*str)
+		return (B_FALSE);
+
 	for (; *str; str++)
 		if (!(isdigit(*str) || (*str == '.')))
 			return (B_FALSE);