diff --git a/lib/url.c b/lib/url.c
index b7e58e1004..00b8a2b086 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -2762,11 +2762,13 @@ static CURLcode parse_remote_port(struct Curl_easy *data,
 
 static bool str_has_ctrl(const char *input)
 {
-  const unsigned char *str = (const unsigned char *)input;
-  while(*str) {
-    if(*str < 0x20)
-      return TRUE;
-    str++;
+  if(input) {
+    const unsigned char *str = (const unsigned char *)input;
+    while(*str) {
+      if(*str < 0x20)
+        return TRUE;
+      str++;
+    }
   }
   return FALSE;
 }