diff --git a/CHANGELOG b/CHANGELOG
index ac3659d..d39ce27 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -39,6 +39,7 @@ xx/xx/2018 autofs-5.1.5
 - better handle hesiod support not built in.
 - fix hesiod string check in master_parse().
 - remove autofs4 module load code.
+- add NULL check in prepare_attempt_prefix().
 
 19/12/2017 autofs-5.1.4
 - fix spec file url.
diff --git a/lib/log.c b/lib/log.c
index f6ab77c..41f95fe 100644
--- a/lib/log.c
+++ b/lib/log.c
@@ -44,6 +44,8 @@ static char *prepare_attempt_prefix(const char *msg)
 
 		snprintf(buffer, ATTEMPT_ID_SIZE, "%02lx", *attempt_id);
 		prefixed_msg = (char *) calloc(len, sizeof(char));
+		if (!prefixed_msg)
+			return NULL;
 		strcpy(prefixed_msg, buffer);
 		strcat(prefixed_msg, "|");
 		strcat(prefixed_msg, msg);