diff --git a/BasiliskII/src/Unix/acconfig.h b/BasiliskII/src/Unix/acconfig.h
index 1c7c1d00..d3abf0a6 100644
--- a/BasiliskII/src/Unix/acconfig.h
+++ b/BasiliskII/src/Unix/acconfig.h
@@ -1,4 +1,4 @@
 /* Additional defines for autoheader. */
 
 /* Define to 'off_t' if <sys/types.h> doesn't define. */
-/* #undef loff_t */
+#undef loff_t
diff --git a/BasiliskII/src/Unix/config.h.in b/BasiliskII/src/Unix/config.h.in
index 775e15b9..5b1eba6f 100644
--- a/BasiliskII/src/Unix/config.h.in
+++ b/BasiliskII/src/Unix/config.h.in
@@ -29,7 +29,7 @@
 #undef X_DISPLAY_MISSING
 
 /* Define to 'off_t' if <sys/types.h> doesn't define. */
-/* #undef loff_t */
+#undef loff_t
 
 /* The number of bytes in a int.  */
 #undef SIZEOF_INT