diff --git a/contrib/tsearch/query.c b/contrib/tsearch/query.c
index 88b7f7e4cb..c0e2cae916 100644
--- a/contrib/tsearch/query.c
+++ b/contrib/tsearch/query.c
@@ -10,6 +10,7 @@
  */
 #include "postgres.h"
 
+#include <ctype.h>
 #include <float.h>
 
 #include "access/gist.h"