diff --git a/tools/cli/files.go b/tools/cli/files.go
index f3107f8e5..963c2b31c 100644
--- a/tools/cli/files.go
+++ b/tools/cli/files.go
@@ -156,7 +156,7 @@ func fname_based_completer(prefix, cwd string, is_match func(string) bool) []str
 			entries, err := os.ReadDir(entry.Abspath)
 			if err == nil {
 				for _, e := range entries {
-					if is_match(e.Name()) || is_dir_or_symlink_to_dir(e, filepath.Join(entry.Abspath, e.Name())) {
+					if is_match(strings.ToLower(e.Name())) || is_dir_or_symlink_to_dir(e, filepath.Join(entry.Abspath, e.Name())) {
 						ans = append(ans, entry.CompletionCandidate)
 						return
 					}
diff --git a/tools/cli/files_test.go b/tools/cli/files_test.go
index 030d4f53e..486b9a19e 100644
--- a/tools/cli/files_test.go
+++ b/tools/cli/files_test.go
@@ -109,6 +109,21 @@ func TestCompleteFiles(t *testing.T) {
 	if len(c.Groups) != 1 || len(c.Groups[0].Matches) != 1 || c.Groups[0].Matches[0].Word != "slink/" {
 		t.Fatalf("Symlink to directory not completed by DirectoryCompleter: %#v", c.Groups)
 	}
+
+	// filenames inside a directory are matched case-insensitively against patterns
+	os.Mkdir(filepath.Join(tdir, "cdir"), 0700)
+	create("cdir", "B.CONF")
+	c = NewCompletions()
+	FnmatchCompleter("", CWD, "*.conf")(c, "c", 0)
+	found := false
+	for _, g := range c.Groups {
+		for _, m := range g.Matches {
+			found = found || m.Word == "cdir/"
+		}
+	}
+	if !found {
+		t.Fatalf("Directory containing only an uppercase extension match not completed by FnmatchCompleter: %#v", c.Groups)
+	}
 }
 
 func TestCompleteExecutables(t *testing.T) {