diff --git a/Python/fmod.c b/Python/fmod.c
index 3ddab75abb1..777166bcb63 100644
--- a/Python/fmod.c
+++ b/Python/fmod.c
@@ -24,12 +24,15 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
 /* Portable fmod(x, y) implementation for systems that don't have it */
 
-#include <math.h>
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "mymath.h"
 #include <errno.h>
 
 double
-fmod(x, y)
-	double x, y;
+fmod(double x, double y)
 {
 	double i, f;