diff --git a/src/libstore/pathlocks.cc b/src/libstore/pathlocks.cc
index b6d8547c..2635e394 100644
--- a/src/libstore/pathlocks.cc
+++ b/src/libstore/pathlocks.cc
@@ -5,6 +5,7 @@
 #include <cerrno>
 #include <cstdlib>
 
+#include <fcntl.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/file.h>