diff --git a/internal/app/ref.go b/internal/app/ref.go
index 20a8051f..ffd5ec58 100644
--- a/internal/app/ref.go
+++ b/internal/app/ref.go
@@ -55,6 +55,10 @@ func parseRef(raw string, kind refKind) (ref, error) {
 	if !hashed {
 		repo, value = "", raw
 	}
+	// Only a repository before # makes a reference, so a branch such as fix#12 stays a branch.
+	if repo != "" && !repositoryLike(repo) {
+		return ref{}, errNotRef
+	}
 	n, err := strconv.ParseInt(value, 10, 64)
 	if err != nil && !hashed {
 		return ref{}, errNotRef
@@ -65,6 +69,12 @@ func parseRef(raw string, kind refKind) (ref, error) {
 	return ref{Number: n, Repo: repo}, nil
 }
 
+// repositoryLike reports whether raw has the form OWNER/REPO or HOST/OWNER/REPO.
+func repositoryLike(raw string) bool {
+	pieces := strings.Split(raw, "/")
+	return len(pieces) >= 2 && settings.ValidSlug(strings.Join(pieces[len(pieces)-2:], "/"))
+}
+
 func parseRefURL(raw string, kind refKind) (ref, error) {
 	invalid := clierr.Wrap(clierr.Usage, fmt.Errorf("%q is not %s URL; use %s", raw, kind.article(), kind.forms()))
 	u, err := url.Parse(raw)
diff --git a/internal/app/ref_test.go b/internal/app/ref_test.go
index 814569e5..0d74c411 100644
--- a/internal/app/ref_test.go
+++ b/internal/app/ref_test.go
@@ -26,7 +26,6 @@ func TestParseRefAcceptsNumbersQualifiedNumbersAndURLs(t *testing.T) {
 		{raw: " 12 ", want: ref{Number: 12}},
 		{raw: "alice/project#12", want: ref{Number: 12, Repo: "alice/project"}},
 		{raw: "localhost:3001/alice/project#12", want: ref{Number: 12, Repo: "localhost:3001/alice/project"}},
-		{raw: "project#12", want: ref{Number: 12, Repo: "project"}},
 		{raw: "https://gitea.com/alice/project/issues/3", want: ref{Number: 3, Repo: "https://gitea.com/alice/project"}},
 		{raw: "https://gitea.com/alice/project/issues/3#issuecomment-79", want: ref{Number: 3, Repo: "https://gitea.com/alice/project"}},
 		{raw: "http://localhost:3001/base/alice/project/pulls/7/files?style=split", kind: pullRef, want: ref{Number: 7, Repo: "http://localhost:3001/base/alice/project"}},
@@ -52,7 +51,7 @@ func TestParseRefAcceptsNumbersQualifiedNumbersAndURLs(t *testing.T) {
 		require.NoError(t, err, tc.raw)
 		require.Equal(t, tc.want, got, tc.raw)
 	}
-	for _, branch := range []string{"feature/login", "bob:fix", "main"} {
+	for _, branch := range []string{"feature/login", "bob:fix", "main", "fix#12", "project#12", "bob:fix#3"} {
 		_, err := parseRef(branch, pullRef)
 		require.ErrorIs(t, err, errNotRef, branch)
 	}
@@ -164,6 +163,7 @@ func TestPullSelectorAcceptsNumbersURLsAndBranches(t *testing.T) {
 		{"bob:fix", 17, ""},
 		{"alice:fix", 0, `no open pull request for branch "alice:fix" in alice/project; pass a number, URL or branch`},
 		{"carol:dup", 21, ""},
+		{"fix#12", 0, `no open pull request for branch "fix#12" in alice/project`},
 		{"dup", 0, "several open pull requests"},
 		{serverURL + "/alice/project", 0, "is not a pull request URL"},
 	} {