diff --git a/util/ack/data.c b/util/ack/data.c
index 181e034dc..2a6946597 100644
--- a/util/ack/data.c
+++ b/util/ack/data.c
@@ -6,15 +6,11 @@
 #include "list.h"
 #include "trans.h"
 
-#ifndef NORCSID
-static char rcs_id[] = "$Id$" ;
-#endif
-
-#undef EXTERN
-#define EXTERN
-
+/* Include once without redefining EXTERN, to declare all the symbols as extern. */
 #include "data.h"
 
-#ifndef NORCSID
-static char rcs_data[] = RCS_DATA ;
-#endif
+/* And again without EXTERN, to define them here. Without the extern versions above
+ * then these symbols will all end up as COMMON, which is poorly supported on OSX. */
+#undef EXTERN
+#define EXTERN
+#include "data.h"
diff --git a/util/ack/data.h b/util/ack/data.h
index ea845c4f7..faa094c0d 100644
--- a/util/ack/data.h
+++ b/util/ack/data.h
@@ -2,9 +2,8 @@
  * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
  * See the copyright notice in the ACK home directory, in the file "Copyright".
  */
-#ifndef NORCSID
-#define RCS_DATA "$Id$"
-#endif
+
+/* WARNING: don't put guards around this file (there are reasons). See data.c. */
 
 EXTERN  char            *stopsuffix;    /* Suffix to stop at */
 EXTERN  char            *machine;       /* The machine id */