diff --git a/CHANGES.rst b/CHANGES.rst
index a383f3f4..930fd7e8 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -20,6 +20,8 @@ Unreleased
     (`#3059`_)
 -   :func:`send_file` supports :class:`~io.BytesIO` partial content.
     (`#2957`_)
+-   :func:`open_resource` accepts the "rt" file mode. This still does
+    the same thing as "r". (:issue:`3163`)
 
 .. _#2935: https://github.com/pallets/flask/issues/2935
 .. _#2957: https://github.com/pallets/flask/issues/2957
diff --git a/docs/conf.py b/docs/conf.py
index f494ea8d..e263d01a 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -18,6 +18,7 @@ extensions = [
     "sphinx.ext.intersphinx",
     "sphinxcontrib.log_cabinet",
     "pallets_sphinx_themes",
+    "sphinx_issues",
 ]
 intersphinx_mapping = {
     "python": ("https://docs.python.org/3/", None),
@@ -29,6 +30,7 @@ intersphinx_mapping = {
     "wtforms": ("https://wtforms.readthedocs.io/en/stable/", None),
     "blinker": ("https://pythonhosted.org/blinker/", None),
 }
+issues_github_path = "pallets/flask"
 
 # HTML -----------------------------------------------------------------
 
diff --git a/docs/requirements.txt b/docs/requirements.txt
index e667deaa..6443d592 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,3 +1,4 @@
 Sphinx~=1.8.0
 Pallets-Sphinx-Themes~=1.1.0
 sphinxcontrib-log-cabinet~=1.0.0
+sphinx-issues~=1.2.0
diff --git a/flask/helpers.py b/flask/helpers.py
index 19cb4c99..c5e85a02 100644
--- a/flask/helpers.py
+++ b/flask/helpers.py
@@ -1053,10 +1053,12 @@ class _PackageBoundObject(object):
 
         :param resource: the name of the resource.  To access resources within
                          subfolders use forward slashes as separator.
-        :param mode: resource file opening mode, default is 'rb'.
+        :param mode: Open file in this mode. Only reading is supported,
+            valid values are "r" (or "rt") and "rb".
         """
-        if mode not in ("r", "rb"):
+        if mode not in {"r", "rt", "rb"}:
             raise ValueError("Resources can only be opened for reading")
+
         return open(os.path.join(self.root_path, resource), mode)
 
 
diff --git a/tests/test_helpers.py b/tests/test_helpers.py
index d65a5f5e..cddc7517 100644
--- a/tests/test_helpers.py
+++ b/tests/test_helpers.py
@@ -1014,6 +1014,7 @@ class TestSafeJoin(object):
                 print(flask.safe_join(*args))
 
 
+
 class TestHelpers(object):
     @pytest.mark.parametrize(
         "debug, expected_flag, expected_default_flag",
@@ -1060,3 +1061,17 @@ class TestHelpers(object):
             assert rv.status_code == 200
             assert rv.data == b"Hello"
             assert rv.mimetype == "text/html"
+
+    @pytest.mark.parametrize("mode", ("r", "rb", "rt"))
+    def test_open_resource(self, mode):
+        app = flask.Flask(__name__)
+
+        with app.open_resource("static/index.html", mode) as f:
+            assert "<h1>Hello World!</h1>" in str(f.read())
+
+    @pytest.mark.parametrize("mode", ("w", "x", "a", "r+"))
+    def test_open_resource_exceptions(self, mode):
+        app = flask.Flask(__name__)
+
+        with pytest.raises(ValueError):
+            app.open_resource("static/index.html", mode)