diff --git a/src/common/processing.h b/src/common/processing.h
index fa9f8e503..7b9f373fd 100644
--- a/src/common/processing.h
+++ b/src/common/processing.h
@@ -2,6 +2,10 @@
 
 #include "util/FFstrbuf.h"
 
+#ifndef _WIN32
+#include <sys/types.h> // pid_t
+#endif
+
 typedef struct FFProcessHandle {
     #if _WIN32
     void* pid; // HANDLE