diff --git a/commit.c b/commit.c
index a575564a15..26c1d5406d 100644
--- a/commit.c
+++ b/commit.c
@@ -341,6 +341,13 @@ int parse_commit(struct commit *item)
 	return ret;
 }
 
+void parse_commit_or_die(struct commit *item)
+{
+	if (parse_commit(item))
+		die("unable to parse commit %s",
+		    item ? sha1_to_hex(item->object.sha1) : "(null)");
+}
+
 int find_commit_subject(const char *commit_buffer, const char **subject)
 {
 	const char *eol;
diff --git a/commit.h b/commit.h
index d912a9d4ac..a3645dabf8 100644
--- a/commit.h
+++ b/commit.h
@@ -49,6 +49,7 @@ struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_n
 
 int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long size);
 int parse_commit(struct commit *item);
+void parse_commit_or_die(struct commit *item);
 
 /* Find beginning and length of commit subject. */
 int find_commit_subject(const char *commit_buffer, const char **subject);
diff --git a/log-tree.c b/log-tree.c
index a49d8e895d..11604b1e5e 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -734,7 +734,7 @@ static int log_tree_diff(struct rev_info *opt, struct commit *commit, struct log
 	if (!opt->diff && !DIFF_OPT_TST(&opt->diffopt, EXIT_WITH_STATUS))
 		return 0;
 
-	parse_commit(commit);
+	parse_commit_or_die(commit);
 	sha1 = commit->tree->object.sha1;
 
 	/* Root commit? */
@@ -759,7 +759,7 @@ static int log_tree_diff(struct rev_info *opt, struct commit *commit, struct log
 			 * parent, showing summary diff of the others
 			 * we merged _in_.
 			 */
-			parse_commit(parents->item);
+			parse_commit_or_die(parents->item);
 			diff_tree_sha1(parents->item->tree->object.sha1,
 				       sha1, "", &opt->diffopt);
 			log_tree_diff_flush(opt);
@@ -774,7 +774,7 @@ static int log_tree_diff(struct rev_info *opt, struct commit *commit, struct log
 	for (;;) {
 		struct commit *parent = parents->item;
 
-		parse_commit(parent);
+		parse_commit_or_die(parent);
 		diff_tree_sha1(parent->tree->object.sha1,
 			       sha1, "", &opt->diffopt);
 		log_tree_diff_flush(opt);