diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -3843,6 +3843,17 @@
 	vn_close(vp, FWRITE, td->td_ucred, td);
 }
 
+static void
+get_corefile_name(char *name, int indexpos, int indexlen, int index)
+{
+	char ch;
+
+	ch = name[indexpos + indexlen];
+	snprintf(name + indexpos, indexlen + 1, "%.*u", indexlen,
+	    index);
+	name[indexpos + indexlen] = ch;
+}
+
 /*
  * If the core format has a %I in it, then we need to check
  * for existing corefiles before defining a name.
@@ -3857,8 +3868,7 @@
 	struct vnode *oldvp, *nextvp, *vp;
 	struct vattr vattr;
 	struct nameidata nd;
-	int error, i, flags, oflags, cmode;
-	char ch;
+	int error, i, flags, oflags, cmode, chosen = -1;
 	struct timespec lasttime;
 
 	nextvp = oldvp = NULL;
@@ -3869,10 +3879,7 @@
 	for (i = 0; i < ncores; i++) {
 		flags = O_CREAT | FWRITE | O_NOFOLLOW;
 
-		ch = name[indexpos + indexlen];
-		(void)snprintf(name + indexpos, indexlen + 1, "%.*u", indexlen,
-		    i);
-		name[indexpos + indexlen] = ch;
+		get_corefile_name(name, indexpos, indexlen, i);
 
 		NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name);
 		error = vn_open_cred(&nd, &flags, cmode, oflags, td->td_ucred,
@@ -3883,6 +3890,7 @@
 		vp = nd.ni_vp;
 		NDFREE_PNBUF(&nd);
 		if ((flags & O_CREAT) == O_CREAT) {
+			chosen = i;
 			nextvp = vp;
 			break;
 		}
@@ -3902,11 +3910,16 @@
 			oldvp = vp;
 			VOP_UNLOCK(oldvp);
 			lasttime = vattr.va_mtime;
+			chosen = i;
 		} else {
 			vnode_close_locked(td, vp);
 		}
 	}
 
+	if (chosen != -1) {
+		get_corefile_name(name, indexpos, indexlen, chosen);
+	}
+
 	if (oldvp != NULL) {
 		if (nextvp == NULL) {
 			if ((td->td_proc->p_flag & P_SUGID) != 0) {