diff --git a/clients/upsclient.h b/clients/upsclient.h
index a07a5cc70d..197ef503ef 100644
--- a/clients/upsclient.h
+++ b/clients/upsclient.h
@@ -53,6 +53,10 @@
 # endif
 #endif
 
+#if defined HAVE_SYS_TYPES_H
+  #include <sys/types.h>
+#endif
+
 #ifdef __cplusplus
 /* *INDENT-OFF* */
 extern "C" {