diff --git a/WHATS_NEW_DM b/WHATS_NEW_DM
index 7f0807a4e..7c9daeeec 100644
--- a/WHATS_NEW_DM
+++ b/WHATS_NEW_DM
@@ -1,5 +1,6 @@
 Version 1.02.28 - 
 ================================
+  Extend deptree buffers so the largest possible device numbers fit.
   Added generation of the versioned libdevmapper-event.so for LVM's test
   Underline longer report help text headings.
 
diff --git a/libdm/libdevmapper.h b/libdm/libdevmapper.h
index b62b4d90f..2f76552e3 100644
--- a/libdm/libdevmapper.h
+++ b/libdm/libdevmapper.h
@@ -181,8 +181,9 @@ int dm_task_add_target(struct dm_task *dmt,
 		       uint64_t size, const char *ttype, const char *params);
 
 /*
- * Format major/minor numbers correctly for input to driver
+ * Format major/minor numbers correctly for input to driver.
  */
+#define DM_FORMAT_DEV_BUFSIZE	13	/* Minimum bufsize to handle worst case. */
 int dm_format_dev(char *buf, int bufsize, uint32_t dev_major, uint32_t dev_minor);
 
 /* Use this to retrive target information returned from a STATUS call */
diff --git a/libdm/libdm-deptree.c b/libdm/libdm-deptree.c
index c73ed50f4..8c4797d9e 100644
--- a/libdm/libdm-deptree.c
+++ b/libdm/libdm-deptree.c
@@ -1243,7 +1243,7 @@ static int _emit_areas_line(struct dm_task *dmt __attribute((unused)),
 			    size_t paramsize, int *pos)
 {
 	struct seg_area *area;
-	char devbuf[10];
+	char devbuf[DM_FORMAT_DEV_BUFSIZE];
 	int tw;
 	const char *prefix = "";
 
@@ -1270,7 +1270,8 @@ static int _emit_segment_line(struct dm_task *dmt, struct load_segment *seg, uin
         int pos = 0;
 	int tw;
         int r;
-	char originbuf[10], cowbuf[10], logbuf[10];
+	char originbuf[DM_FORMAT_DEV_BUFSIZE], cowbuf[DM_FORMAT_DEV_BUFSIZE];
+	char logbuf[DM_FORMAT_DEV_BUFSIZE];
 	const char *logtype;
 
 	switch(seg->type) {