diff --git a/appl/popper/popper.h b/appl/popper/popper.h
index d86d3599e..8835a0de4 100644
--- a/appl/popper/popper.h
+++ b/appl/popper/popper.h
@@ -80,6 +80,7 @@
 #endif
 #include "version.h"
 
+#include <err.h>
 #include <roken.h>
 
 #define KERBEROS