diff --git a/commit-graph.c b/commit-graph.c
index d1c98681e8..63a56483cf 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -116,12 +116,10 @@ timestamp_t commit_graph_generation(const struct commit *c)
 	struct commit_graph_data *data =
 		commit_graph_data_slab_peek(&commit_graph_data_slab, c);
 
-	if (!data)
-		return GENERATION_NUMBER_INFINITY;
-	else if (data->graph_pos == COMMIT_NOT_FROM_GRAPH)
-		return GENERATION_NUMBER_INFINITY;
+	if (data && data->generation)
+		return data->generation;
 
-	return data->generation;
+	return GENERATION_NUMBER_INFINITY;
 }
 
 static struct commit_graph_data *commit_graph_data_at(const struct commit *c)
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index 049c5fc8ea..b6e1211578 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -630,7 +630,7 @@ test_expect_success 'detect incorrect generation number' '
 
 test_expect_success 'detect incorrect generation number' '
 	corrupt_graph_and_verify $GRAPH_BYTE_COMMIT_GENERATION "\01" \
-		"non-zero generation number"
+		"commit-graph generation for commit"
 '
 
 test_expect_success 'detect incorrect commit date' '