diff --git a/lib/com_err/com_err.c b/lib/com_err/com_err.c
index 22a810f8f..52f6e2e43 100644
--- a/lib/com_err/com_err.c
+++ b/lib/com_err/com_err.c
@@ -38,6 +38,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <roken.h>
+#include <heim_threads.h>
 #include "com_err.h"
 
 struct et_list *_et_list = NULL;
@@ -132,7 +133,7 @@ reset_com_err_hook (void)
 static const char char_set[] =
         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_";
 
-static char buf[6];
+static HEIMDAL_THREAD_LOCAL char buf[6];
 
 KRB5_LIB_FUNCTION const char * KRB5_LIB_CALL
 error_table_name(int num)