diff --git a/src/cli.c b/src/cli.c
index 62c2467..b8c6aec 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -1120,7 +1120,7 @@ cli_build_asset(char *fpath, struct dirent *dp)
 
 	/* Replace dots, spaces, etc etc with underscores. */
 	for (p = name; *p != '\0'; p++) {
-		if (*p == '.' || isspace(*p) || *p == '-')
+		if (*p == '.' || isspace((unsigned char)*p) || *p == '-')
 			*p = '_';
 	}
 
diff --git a/src/http.c b/src/http.c
index 82f5992..d8fef25 100644
--- a/src/http.c
+++ b/src/http.c
@@ -1002,7 +1002,8 @@ http_argument_urldecode(char *arg)
 			return (KORE_RESULT_ERROR);
 		}
 
-		if (!isxdigit(*(p + 1)) || !isxdigit(*(p + 2))) {
+		if (!isxdigit((unsigned char)*(p + 1)) ||
+		    !isxdigit((unsigned char)*(p + 2))) {
 			*in++ = *p++;
 			continue;
 		}