Index: sys/geom/label/g_label_ufs.c
===================================================================
--- sys/geom/label/g_label_ufs.c
+++ sys/geom/label/g_label_ufs.c
@@ -48,6 +48,39 @@
 #define	G_LABEL_UFS_VOLUME	0
 #define	G_LABEL_UFS_ID		1
 
+/*
+ * G_LABEL_UFS_CMP returns true if difference between provider mediasize
+ * and filesystem size is less than G_LABEL_UFS_MAXDIFF sectors
+ */
+#define	G_LABEL_UFS_CMP(prov, fsys, size) 				   \
+	( abs( ((fsys)->size) - ( (prov)->mediasize / (fsys)->fs_fsize ))  \
+				< G_LABEL_UFS_MAXDIFF )
+#define	G_LABEL_UFS_MAXDIFF	0x100
+
+/*
+ * For MBR and EBR we need to check if file system size is almost equal to
+ * providers size, because sysinstall(8) used to bogusly put first partition
+ * at offset 0 instead of 16, and glabel/ufs would find file system on slice
+ * instead of partition.
+ *
+ * In addition, media size can be a bit bigger than file system size. For
+ * instance, mkuzip can append bytes to align data to large sector size (it
+ * improves compression rates).
+ */
+static bool
+g_label_ufs_ignore_possible_bsdlabel_slice(struct g_provider *pp,
+    struct fs *fs)
+{
+	const char *provider_name = pp->geom->class->name;
+
+	if (strcmp(provider_name, "MBR") == 0 ||
+	    strcmp(provider_name, "EBR") == 0)
+		return (!G_LABEL_UFS_CMP(pp, fs, fs_old_size) &&
+		    !G_LABEL_UFS_CMP(pp, fs, fs_providersize));
+
+	return (true);
+}
+
 /*
  * Try to find a superblock on the provider. If successful, look for a volume
  * label and create an appropriate provider based on that.
@@ -78,6 +111,9 @@
 	} else {
 		goto out;
 	}
+	/* Check if this should be ignored for compatibility. */
+	if (g_label_ufs_ignore_possible_bsdlabel_slice(pp, fs))
+		goto out;
 	G_LABEL_DEBUG(1, "%s file system detected on %s.",
 	    fs->fs_magic == FS_UFS1_MAGIC ? "UFS1" : "UFS2", pp->name);
 	switch (what) {