diff --git a/include/rngxx/internal/common.h b/include/rngxx/internal/common.h
index 076db3c..254b4cf 100644
--- a/include/rngxx/internal/common.h
+++ b/include/rngxx/internal/common.h
@@ -8,6 +8,8 @@ extern "C" {
 #include <stdint.h>
 #include <stddef.h>
 
+#include <sys/types.h>
+
 #ifndef _RNGXX_COMMON_MINIMAL
 #include <stdlib.h>