diff --git a/_webp.c b/_webp.c
index 421f49957..3ba8fcb9a 100644
--- a/_webp.c
+++ b/_webp.c
@@ -247,7 +247,7 @@ PyObject* WebPDecoderVersion_wrapper(PyObject* self, PyObject* args){
  * The version of webp that ships with (0.1.3) Ubuntu 12.04 doesn't handle alpha well.
  * Files that are valid with 0.3 are reported as being invalid.
  */
-int WebPDecoderBuggyAlpha() {
+int WebPDecoderBuggyAlpha(void) {
     return WebPGetDecoderVersion()==0x0103;
 }