diff --git a/ChangeLog b/ChangeLog
index 5e9c473c..bccd22d6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2014-05-16  Joerg Wunsch <j.gnu@uriah.heep.sax.de>
+
+	* dfu.c (dfu_open, dfu_init): Fix signature of the dummy functions
+	(in the !HAVE_LIBUSB case) to match prototypes.
+
 2014-05-16  Joerg Wunsch <j.gnu@uriah.heep.sax.de>
 
 	* avr910.c: Replace all occurences of exit() in potential library
diff --git a/dfu.c b/dfu.c
index d88743e5..75632f65 100644
--- a/dfu.c
+++ b/dfu.c
@@ -36,13 +36,13 @@
 
 #ifndef HAVE_LIBUSB
 
-int dfu_open(struct dfu_dev *dfu, char *port_name) {
+struct dfu_dev *dfu_open(char *port_name) {
   fprintf(stderr, "%s: Error: No USB support in this compile of avrdude\n",
     progname);
-  return -1;
+  return NULL;
 }
 
-int dfu_init(struct dfu_dev *dfu, unsigned short usb_pid) {
+int dfu_init(struct dfu_dev *dfu, unsigned short usb_vid, unsigned short usb_pid) {
   return -1;
 }