diff --git a/apps/restconf/restconf_evhtp.c b/apps/restconf/restconf_evhtp.c
index b69eba42..49245afd 100644
--- a/apps/restconf/restconf_evhtp.c
+++ b/apps/restconf/restconf_evhtp.c
@@ -396,7 +396,7 @@ restconf_evhtp_reply(restconf_conn        *rc,
      * [RFC7231]).
      */
     if (sd->sd_code != 204 && sd->sd_code > 199)
-	if (restconf_reply_header(sd, "Content-Length", "%lu", sd->sd_body_len) < 0)
+	if (restconf_reply_header(sd, "Content-Length", "%zu", sd->sd_body_len) < 0)
 	    goto done;	
     /* Create reply and write headers */
     if (native_send_reply(rc, sd, req) < 0)
diff --git a/apps/restconf/restconf_main_native.c b/apps/restconf/restconf_main_native.c
index 5e7551f2..4bbe7b47 100644
--- a/apps/restconf/restconf_main_native.c
+++ b/apps/restconf/restconf_main_native.c
@@ -265,7 +265,7 @@ buf_write(char   *buf,
 	}
 	memcpy(dbgstr, buf, sz);
 	dbgstr[sz] = '\0';
-	clicon_debug(1, "%s buflen:%lu buf:%s", __FUNCTION__, buflen, dbgstr);
+	clicon_debug(1, "%s buflen:%zu buf:%s", __FUNCTION__, buflen, dbgstr);
 	free(dbgstr);
     }
     while (totlen < buflen){
@@ -641,7 +641,7 @@ send_badrequest(clicon_handle       h,
     cprintf(cb, "HTTP/1.1 400 Bad Request\r\nConnection: close\r\n");
     if (body){
 	cprintf(cb, "Content-Type: %s\r\n", media);
-	cprintf(cb, "Content-Length: %lu\r\n", strlen(body));
+	cprintf(cb, "Content-Length: %u\r\n", strlen(body));
     }
     else
 	cprintf(cb, "Content-Length: 0\r\n");
@@ -703,7 +703,7 @@ restconf_connection(int   s,
 	    */
 	    if ((n = SSL_read(rc->rc_ssl, buf, sizeof(buf))) < 0){
 		sslerr = SSL_get_error(rc->rc_ssl, n);
-		clicon_debug(1, "%s SSL_read() n:%ld errno:%d sslerr:%d", __FUNCTION__, n, errno, sslerr);
+		clicon_debug(1, "%s SSL_read() n:%zd errno:%d sslerr:%d", __FUNCTION__, n, errno, sslerr);
 		switch (sslerr){
 		case SSL_ERROR_WANT_READ:            /* 2 */
 		    /* SSL_ERROR_WANT_READ is returned when the last operation was a read operation 
@@ -745,10 +745,10 @@ restconf_connection(int   s,
 		continue;
 	    }
 	}
-	clicon_debug(1, "%s read:%ld", __FUNCTION__, n);
+	clicon_debug(1, "%s (ssl)read:%zd", __FUNCTION__, n);
 	if (n == 0){
 	    clicon_debug(1, "%s n=0 closing socket", __FUNCTION__);
-	    if (restconf_close_ssl_socket(rc, 1) < 0)
+	    if (restconf_close_ssl_socket(rc, 0) < 0)
 		goto done;
 	    restconf_conn_free(rc);    
 	    rc = NULL;
diff --git a/apps/restconf/restconf_nghttp2.c b/apps/restconf/restconf_nghttp2.c
index 7f963c51..698e1a6e 100644
--- a/apps/restconf/restconf_nghttp2.c
+++ b/apps/restconf/restconf_nghttp2.c
@@ -184,7 +184,7 @@ session_send_callback(nghttp2_session *session,
     SSL           *ssl; 
     int            sslerr;
     
-    clicon_debug(1, "%s buflen:%lu", __FUNCTION__, buflen);
+    clicon_debug(1, "%s buflen:%zu", __FUNCTION__, buflen);
     s = rc->rc_s;
     ssl = rc->rc_ssl;
     while (totlen < buflen){
@@ -259,7 +259,7 @@ session_send_callback(nghttp2_session *session,
 	clicon_debug(1, "%s retval:%d", __FUNCTION__, retval);
 	return retval;
     }
-    clicon_debug(1, "%s retval:%lu", __FUNCTION__, totlen);
+    clicon_debug(1, "%s retval:%zd", __FUNCTION__, totlen);
     return totlen;
 }
 
@@ -379,7 +379,7 @@ restconf_sd_read(nghttp2_session     *session,
 #endif
     assert(cbuf_len(cb) > sd->sd_body_offset);
     remain = cbuf_len(cb) - sd->sd_body_offset;
-    clicon_debug(1, "%s length:%lu totlen:%d, offset:%lu remain:%lu",
+    clicon_debug(1, "%s length:%zu totlen:%d, offset:%zu remain:%zu",
 		 __FUNCTION__,
 		 length,
 		 cbuf_len(cb),
@@ -395,7 +395,7 @@ restconf_sd_read(nghttp2_session     *session,
     }
     memcpy(buf, cbuf_get(cb) + sd->sd_body_offset, len);
     sd->sd_body_offset += len;
-    clicon_debug(1, "%s retval:%lu", __FUNCTION__, len);
+    clicon_debug(1, "%s retval:%zu", __FUNCTION__, len);
     return len;
 }
 
@@ -483,7 +483,7 @@ http2_exec(restconf_conn        *rc,
      * [RFC7231]).
      */
     if (sd->sd_code != 204 && sd->sd_code > 199)
-	if (restconf_reply_header(sd, "Content-Length", "%lu", sd->sd_body_len) < 0)
+	if (restconf_reply_header(sd, "Content-Length", "%zu", sd->sd_body_len) < 0)
 	    goto done;	
     if (sd->sd_code){
 	if (restconf_submit_response(session, rc, stream_id, sd) < 0)
@@ -835,6 +835,20 @@ on_extension_chunk_recv_callback(nghttp2_session *session,
     return 0;
 }
 
+/*! Library provides the error code, and message for debugging purpose.
+ */
+static int
+error_callback(nghttp2_session *session,
+	       const char *msg,
+	       size_t len,
+	       void *user_data)
+{
+    //    restconf_conn *rc = (restconf_conn *)user_data;
+    clicon_debug(1, "%s", __FUNCTION__);
+    return 0;
+}
+
+#if (NGHTTP2_VERSION_NUM > 0x011201) /* Unsure of version number */
 /*! Library provides the error code, and message for debugging purpose.
  */
 static int
@@ -849,6 +863,7 @@ error_callback2(nghttp2_session *session,
     clicon_err(OE_NGHTTP2, lib_error_code, "%s", msg);
     return 0;
 }
+#endif
 
 /*
  * XXX see session_recv
@@ -944,7 +959,10 @@ http2_session_init(restconf_conn *rc)
     nghttp2_session_callbacks_set_unpack_extension_callback(callbacks, unpack_extension_callback);
 #endif
     nghttp2_session_callbacks_set_on_extension_chunk_recv_callback(callbacks, on_extension_chunk_recv_callback);
+    nghttp2_session_callbacks_set_error_callback(callbacks, error_callback);
+#if (NGHTTP2_VERSION_NUM > 0x011201) /* Unsure of version number */
     nghttp2_session_callbacks_set_error_callback2(callbacks, error_callback2);
+#endif
 
     /* Create session for server use, register callbacks */
     if ((ngerr = nghttp2_session_server_new3(&session, callbacks, rc, NULL, NULL)) < 0){