diff --git a/src/synth/synth_debug.c b/src/synth/synth_debug.c
index 6359a0e..475eabc 100644
--- a/src/synth/synth_debug.c
+++ b/src/synth/synth_debug.c
@@ -5,7 +5,7 @@
 #include <windows.h>
 #endif
 #include <stdarg.h>
-
+#include <stdio.h>
 
 // --------------------------------------------------------------
 // internal funcs