diff --git a/src/webp.cc b/src/webp.cc
index 7b6d839..45566dd 100644
--- a/src/webp.cc
+++ b/src/webp.cc
@@ -218,8 +218,8 @@ void *a_Webp_new(DilloImage *Image, DilloUrl *url, int version)
 
 #else /* ENABLE_WEBP */
 
-void *a_Webp_new() { return 0; }
-void a_Webp_callback() { return; }
+void *a_Webp_new(DilloImage *, DilloUrl *, int) { return 0; }
+void a_Webp_callback(int Op, void *data) { return; }
 const char *a_Webp_version(char *buf, int n) { return 0; }
 
 #endif /* ENABLE_WEBP */