diff -Naur WaveGain-1.3.1/wavegain.c WaveGain-1.3.1-p/wavegain.c
--- WaveGain-1.3.1/wavegain.c	2011-12-19 14:43:22.000000000 +0100
+++ WaveGain-1.3.1-p/wavegain.c	2019-06-07 11:07:16.903676452 +0200
@@ -22,6 +22,8 @@
 #include <string.h>
 #include <time.h>
 #include <ctype.h>
+#include <sys/types.h>
+#include <unistd.h>
 
 #ifdef _WIN32
 #include <io.h>