diff --git a/instrumentation/opentelemetry-instrumentation-wsgi/src/opentelemetry/instrumentation/wsgi/__init__.py b/instrumentation/opentelemetry-instrumentation-wsgi/src/opentelemetry/instrumentation/wsgi/__init__.py
index f1cbbfebd6..9253251eba 100644
--- a/instrumentation/opentelemetry-instrumentation-wsgi/src/opentelemetry/instrumentation/wsgi/__init__.py
+++ b/instrumentation/opentelemetry-instrumentation-wsgi/src/opentelemetry/instrumentation/wsgi/__init__.py
@@ -229,9 +229,7 @@ def capture_custom_request_headers(environ, attributes):
     )
     for header_name in custom_request_headers:
         wsgi_env_var = header_name.upper().replace("-", "_")
-        header_values = environ.get(
-            "HTTP_{wsgi_env_var}".format(wsgi_env_var=wsgi_env_var)
-        )
+        header_values = environ.get(f"HTTP_{wsgi_env_var}")
 
         if header_values:
             key = normalise_request_header_name(header_name)
diff --git a/util/opentelemetry-util-http/src/opentelemetry/util/http/__init__.py b/util/opentelemetry-util-http/src/opentelemetry/util/http/__init__.py
index 7d53898008..df051b85a5 100644
--- a/util/opentelemetry-util-http/src/opentelemetry/util/http/__init__.py
+++ b/util/opentelemetry-util-http/src/opentelemetry/util/http/__init__.py
@@ -104,15 +104,13 @@ def remove_url_credentials(url: str) -> str:
 
 
 def normalise_request_header_name(header):
-    return "http.request.header.{key}".format(
-        key=header.lower().replace("-", "_")
-    )
+    key = header.lower().replace("-", "_")
+    return f"http.request.header.{key}"
 
 
 def normalise_response_header_name(header):
-    return "http.response.header.{key}".format(
-        key=header.lower().replace("-", "_")
-    )
+    key=header.lower().replace("-", "_")
+    return f"http.response.header.{key}"
 
 
 def get_custom_headers(env_var):
diff --git a/util/opentelemetry-util-http/tests/test_capture_custom_headers.py b/util/opentelemetry-util-http/tests/test_capture_custom_headers.py
index b07f50eeaf..dd134c21b5 100644
--- a/util/opentelemetry-util-http/tests/test_capture_custom_headers.py
+++ b/util/opentelemetry-util-http/tests/test_capture_custom_headers.py
@@ -33,7 +33,7 @@ def test_get_custom_request_header(self):
         custom_headers_to_capture = get_custom_headers(
             OTEL_PYTHON_CAPTURE_REQUEST_HEADERS
         )
-        assert custom_headers_to_capture == ["User-Agent", "Test-Header"]
+        self.assertEqual(custom_headers_to_capture, ["User-Agent", "Test-Header"])
 
     @patch.dict(
         "os.environ",
@@ -45,16 +45,16 @@ def test_get_custom_response_header(self):
         custom_headers_to_capture = get_custom_headers(
             OTEL_PYTHON_CAPTURE_RESPONSE_HEADERS
         )
-        assert custom_headers_to_capture == [
+        self.assertEqual(custom_headers_to_capture, [
             "content-type",
             "content-length",
             "test-header",
-        ]
+        ])
 
     def test_normalise_request_header_name(self):
         key = normalise_request_header_name("Test-Header")
-        assert key == "http.request.header.test_header"
+        self.assertEqual(key, "http.request.header.test_header")
 
     def test_normalise_response_header_name(self):
         key = normalise_response_header_name("Test-Header")
-        assert key == "http.response.header.test_header"
+        self.assertEqual(key, "http.response.header.test_header")