diff --git a/gdc_maf_tool/defer.py b/gdc_maf_tool/defer.py
index 165f852..0fe9e80 100644
--- a/gdc_maf_tool/defer.py
+++ b/gdc_maf_tool/defer.py
@@ -30,21 +30,24 @@ def _realize(self):
 
         response = self._provider()
         response.raise_for_status()
-        self._validate_checksum(response.content)
+        self._validate_checksum(response)
 
         self._content_position = 0
         self._content_length = len(response.content)
         self._response = response
 
-    def _validate_checksum(self, content):
+    def _validate_checksum(self, response):
         if not self._md5sum:
             return
 
         hash_md5 = hashlib.md5()  # nosec
-        hash_md5.update(content)
+        hash_md5.update(response.content)
         md5 = hash_md5.hexdigest()
         if self._md5sum != md5:
-            raise ValueError(f"Failed checksum. Expected {self._md5sum}.  Got {md5}.")
+            raise ValueError(
+                f"Failed checksum for {response.url}. "
+                f"Expected {self._md5sum}. Got {md5}."
+            )
 
     @property
     def response(self) -> requests.Response:
diff --git a/tox.ini b/tox.ini
index c1f9413..acc3c5c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -19,4 +19,4 @@ commands =
     bandit -r gdc_maf_tool/
     bandit -r tests/
     flake8
-    pytest {posargs: -lv tests/ --cov=gdc-maf-tool --cov-report=html}
+    pytest {posargs: -lv tests/ --cov=gdc_maf_tool --cov-report=html}