diff --git a/include/lsquic_types.h b/include/lsquic_types.h
index ff7e4b1..abb3340 100644
--- a/include/lsquic_types.h
+++ b/include/lsquic_types.h
@@ -8,6 +8,7 @@
  */
 
 #include <stdint.h>
+#include <sys/types.h>
 
 #define MAX_CID_LEN 20
 #define GQUIC_CID_LEN 8