diff --git a/src/source.re.c b/src/source.re.c
index ae24589..c613b67 100644
--- a/src/source.re.c
+++ b/src/source.re.c
@@ -50,7 +50,7 @@ static int source_compare(const union line64 a, const union line64 b)
 #define TREE_VALUE size_t /* Index into source list. */
 #define TREE_COMPARE
 #define TREE_TO_STRING
-#define TREE_DEFAULT (size_t)0
+#define TREE_DEFAULT 0
 #include "../src/tree.h"
 
 
@@ -173,10 +173,13 @@ finally:
 /** Lookup the last source in `range` in sources `s`. They are invalidated on
  adding a source, (probably fine.) */
 const struct source *source_lookup(struct sources *const s,
-	const union line64 range) {
-	union line64 line_source;
+	const union line64 x) {
+	struct source_tree_iterator it;
 	assert(s);
-	line_source = source_tree_less_or(&s->dates, range, (union line64){0});
-	sourcemap_table_get(&s->map, line_source);
-	return s->list.data + idx;
+	it = source_tree_less(&s->dates, x);
+	/* If it's before all elements of the journal or is not on the same date as
+	 the source, this has no source, which is `list[0]` by <fn:sources>. */
+	if(!source_tree_has_element(&it)
+		|| x.date.u32 != source_tree_key(&it).date.u32) return s->list.data + 0;
+	return s->list.data + *source_tree_value(&it);
 }