diff --git a/pipeline/packager.py b/pipeline/packager.py
index bd301890..c9ecf6f7 100644
--- a/pipeline/packager.py
+++ b/pipeline/packager.py
@@ -65,7 +65,7 @@ def manifest(self):
     def compiler_options(self):
         return self.config.get("compiler_options", {})
 
-    @lru_cache()
+    @lru_cache
     def get_sri(self, path):
         method = self.config.get("integrity")
         if method not in {"sha256", "sha384", "sha512"}:
@@ -75,7 +75,8 @@ def get_sri(self, path):
                 h = getattr(hashlib, method)()
                 for data in iter(lambda: fd.read(16384), b""):
                     h.update(data)
-            return "%s-%s" % (method, base64.b64encode(h.digest()).decode())
+            digest = base64.b64encode(h.digest()).decode()
+            return f"{method}-{digest}"
         return None
 
 
diff --git a/tests/tests/test_template.py b/tests/tests/test_template.py
index cc685b81..0fc05c02 100644
--- a/tests/tests/test_template.py
+++ b/tests/tests/test_template.py
@@ -121,7 +121,8 @@ def test_sri_sha512(self):
     def get_integrity(path, method):
         with staticfiles_storage.open(path) as fd:
             h = getattr(hashlib, method)(fd.read())
-        return "%s-%s" % (method, base64.b64encode(h.digest()).decode())
+        digest = base64.b64encode(h.digest()).decode()
+        return f"{method}-{digest}"
 
 
 class DjangoTest(TestCase):