diff --git a/WHATS_NEW b/WHATS_NEW
index c932ec558..d5f192b39 100644
--- a/WHATS_NEW
+++ b/WHATS_NEW
@@ -1,5 +1,6 @@
 Version 2.02.78 - 
 ====================================
+  Check reallocated buffer for NULL before use in clvmd do_command().
   Fix memory leak when VG allocation policy in metadata is invalid.
   Ignore unrecognised allocation policy found in metadata instead of aborting.
   Factor out tag printing into _out_tags and avoid leaking string buffer.
diff --git a/daemons/clvmd/clvmd-command.c b/daemons/clvmd/clvmd-command.c
index 3500ca5d9..8d1dcff56 100644
--- a/daemons/clvmd/clvmd-command.c
+++ b/daemons/clvmd/clvmd-command.c
@@ -169,7 +169,8 @@ int do_command(struct local_client *client, struct clvm_header *msg, int msglen,
 
 	/* Check the status of the command and return the error text */
 	if (status) {
-		*retlen = 1 + snprintf(*buf, buflen, "%s", strerror(status));
+		*retlen = 1 + (*buf) ? snprintf(*buf, buflen, "%s",
+						strerror(status)) : -1;
 	}
 
 	return status;