diff --git a/kernel/io.cc b/kernel/io.cc
index 0fdbd3c37..7d812fc74 100644
--- a/kernel/io.cc
+++ b/kernel/io.cc
@@ -4,6 +4,12 @@
 #include <dirent.h>
 #include <string>
 
+#if !defined(WIN32)
+#include <unistd.h>
+#else
+#include <io.h>
+#endif
+
 YOSYS_NAMESPACE_BEGIN
 
 // Set of utilities for handling files