diff --git a/rtc_base/filerotatingstream.cc b/rtc_base/filerotatingstream.cc
index d03ab3937f..b1dc5ff998 100644
--- a/rtc_base/filerotatingstream.cc
+++ b/rtc_base/filerotatingstream.cc
@@ -21,6 +21,7 @@
 #else
 #include <dirent.h>
 #include <sys/stat.h>
+#include <unistd.h>
 #endif  // WEBRTC_WIN
 
 #include "absl/strings/match.h"