diff --git a/diffcore-rename.c b/diffcore-rename.c
index 266d4fae48..41558185ae 100644
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@ -379,7 +379,6 @@ static const char *get_basename(const char *filename)
 	return base ? base + 1 : filename;
 }
 
-MAYBE_UNUSED
 static int find_basename_matches(struct diff_options *options,
 				 int minimum_score)
 {
@@ -716,11 +715,55 @@ void diffcore_rename(struct diff_options *options)
 	if (minimum_score == MAX_SCORE)
 		goto cleanup;
 
-	/* Calculate how many renames are left */
-	num_destinations = (rename_dst_nr - rename_count);
-	remove_unneeded_paths_from_src(want_copies);
 	num_sources = rename_src_nr;
 
+	if (want_copies || break_idx) {
+		/*
+		 * Cull sources:
+		 *   - remove ones corresponding to exact renames
+		 */
+		trace2_region_enter("diff", "cull after exact", options->repo);
+		remove_unneeded_paths_from_src(want_copies);
+		trace2_region_leave("diff", "cull after exact", options->repo);
+	} else {
+		/* Determine minimum score to match basenames */
+		double factor = 0.5;
+		char *basename_factor = getenv("GIT_BASENAME_FACTOR");
+		int min_basename_score;
+
+		if (basename_factor)
+			factor = strtol(basename_factor, NULL, 10)/100.0;
+		assert(factor >= 0.0 && factor <= 1.0);
+		min_basename_score = minimum_score +
+			(int)(factor * (MAX_SCORE - minimum_score));
+
+		/*
+		 * Cull sources:
+		 *   - remove ones involved in renames (found via exact match)
+		 */
+		trace2_region_enter("diff", "cull after exact", options->repo);
+		remove_unneeded_paths_from_src(want_copies);
+		trace2_region_leave("diff", "cull after exact", options->repo);
+
+		/* Utilize file basenames to quickly find renames. */
+		trace2_region_enter("diff", "basename matches", options->repo);
+		rename_count += find_basename_matches(options,
+						      min_basename_score);
+		trace2_region_leave("diff", "basename matches", options->repo);
+
+		/*
+		 * Cull sources, again:
+		 *   - remove ones involved in renames (found via basenames)
+		 */
+		trace2_region_enter("diff", "cull basename", options->repo);
+		remove_unneeded_paths_from_src(want_copies);
+		trace2_region_leave("diff", "cull basename", options->repo);
+	}
+
+	/* Calculate how many rename destinations are left */
+	num_destinations = (rename_dst_nr - rename_count);
+	num_sources = rename_src_nr; /* rename_src_nr reflects lower number */
+
 	/* All done? */
 	if (!num_destinations || !num_sources)
 		goto cleanup;
@@ -751,7 +794,7 @@ void diffcore_rename(struct diff_options *options)
 		struct diff_score *m;
 
 		if (rename_dst[i].is_rename)
-			continue; /* dealt with exact match already. */
+			continue; /* exact or basename match already handled */
 
 		m = &mx[dst_cnt * NUM_CANDIDATE_PER_DST];
 		for (j = 0; j < NUM_CANDIDATE_PER_DST; j++)
diff --git a/t/t4001-diff-rename.sh b/t/t4001-diff-rename.sh
index 0f97858197..99a5d1bd1c 100755
--- a/t/t4001-diff-rename.sh
+++ b/t/t4001-diff-rename.sh
@@ -277,10 +277,11 @@ test_expect_success 'basename similarity vs best similarity' '
 	git add file.txt file.md &&
 	git commit -a -m "rename" &&
 	git diff-tree -r -M --name-status HEAD^ HEAD >actual &&
-	# subdir/file.txt is 88% similar to file.md and 78% similar to file.txt
+	# subdir/file.txt is 88% similar to file.md, 78% similar to file.txt,
+	# but since same basenames are checked first...
 	cat >expected <<-\EOF &&
-	R088	subdir/file.txt	file.md
-	A	file.txt
+	A	file.md
+	R078	subdir/file.txt	file.txt
 	EOF
 	test_cmp expected actual
 '