diff --git a/lib/libc/stdlib/strtonum.c b/lib/libc/stdlib/strtonum.c
index 0bf29c37aaa..6dccd973606 100644
--- a/lib/libc/stdlib/strtonum.c
+++ b/lib/libc/stdlib/strtonum.c
@@ -51,7 +51,7 @@ strtonum(const char *numstr, long long minval, long long maxval,
 		error = INVALID;
 	else {
 		ll = strtoll(numstr, &ep, 10);
-		if (numstr == ep || *ep != '\0')
+		if (errno == EINVAL || numstr == ep || *ep != '\0')
 			error = INVALID;
 		else if ((ll == LLONG_MIN && errno == ERANGE) || ll < minval)
 			error = TOOSMALL;