diff --git a/src/ChangeLog b/src/ChangeLog
index 874ea0486d6..91dc8b6d8c9 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,8 +1,9 @@
 2013-03-05  Paul Eggert  <eggert@cs.ucla.edu>
 
-	Fix a build failure on OpenBSD 4.x.
-	* sysdep.c (KERN_PROC, kinfo_proc) [BSD_SYSTEM && !KERN_PROC]:
-	Define to KERN_PROC2 and kinfo_proc2, for OpenBSD 4.9.
+	Fix a build failure on OpenBSD 4.x and MirBSD.
+	* sysdep.c (KERN_PROC, kinfo_proc)
+	[BSD_SYSTEM && (!KERN_PROC || __MirBSD__)]:
+	Define to KERN_PROC2 and kinfo_proc2, for OpenBSD 4.9 and MirBSD.
 	list-system-processes still returns nil, but at least it doesn't crash.
 	Problem reported by Nelson H. F. Beebe in
 	<http://lists.gnu.org/archive/html/emacs-devel/2013-03/msg00021.html>.
diff --git a/src/sysdep.c b/src/sysdep.c
index 392771bd121..9eba9e86819 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -2650,8 +2650,9 @@ list_system_processes (void)
 #elif defined BSD_SYSTEM
 
 /* OpenBSD 4.9 and earlier do not have KERN_PROC.  Approximate it with
-   KERN_PROC2.  */
-# ifndef KERN_PROC
+   KERN_PROC2.  MirBSD's KERN_PROC seems to be busted.  */
+# if !defined KERN_PROC || defined __MirBSD__
+#  undef KERN_PROC
 #  define KERN_PROC KERN_PROC2
 #  define kinfo_proc kinfo_proc2
 # endif