diff --git a/lib/url.c b/lib/url.c
index e7ef8024658ac073a2d050a828004f4ce7d4a924..8685c61a25de26962de517401b4c00d5bb9898ed 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -683,9 +683,9 @@ CURLcode Curl_open(struct SessionHandle **curl)
     data->set.fread_func = (curl_read_callback)fread;
 
     /* conversion callbacks for non-ASCII hosts */
-    data->set.convfromnetwork = (curl_conv_callback)ZERO_NULL;
-    data->set.convtonetwork   = (curl_conv_callback)ZERO_NULL;
-    data->set.convfromutf8    = (curl_conv_callback)ZERO_NULL;
+    data->set.convfromnetwork = ZERO_NULL;
+    data->set.convtonetwork   = ZERO_NULL;
+    data->set.convfromutf8    = ZERO_NULL;
 
 #if defined(CURL_DOES_CONVERSIONS) && defined(HAVE_ICONV)
     /* conversion descriptors for iconv calls */