diff --git a/appl/popper/popper.h b/appl/popper/popper.h
index 43048332f..f17698e39 100644
--- a/appl/popper/popper.h
+++ b/appl/popper/popper.h
@@ -34,6 +34,7 @@
 #include <fcntl.h>
 #include <pwd.h>
 #include <sys/types.h>
+#include <unistd.h>
 #include <sys/stat.h>
 #include <sys/file.h>
 #include <sys/time.h>