diff --git a/ps/display.c b/ps/display.c
index b1f98bdc..c20285d4 100644
--- a/ps/display.c
+++ b/ps/display.c
@@ -25,6 +25,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <error.h>
 
 #include <sys/sysmacros.h>
 #include <sys/types.h>