diff --git a/testdata/dnn/download_models.py b/testdata/dnn/download_models.py
index 6eca15c29..7cbbd4d40 100755
--- a/testdata/dnn/download_models.py
+++ b/testdata/dnn/download_models.py
@@ -51,7 +51,8 @@ def verify(self):
                         break
                     sha.update(buf)
             print('  actual {}'.format(sha.hexdigest()))
-            return self.sha == sha.hexdigest()
+            self.sha_actual = sha.hexdigest()
+            return self.sha == self.sha_actual
         except Exception as e:
             print('  catch {}'.format(e))
 
@@ -82,7 +83,10 @@ def get(self):
 
         print(' done')
         print(' file {}'.format(self.filename))
-        return self.verify()
+        candidate_verify = self.verify()
+        if not candidate_verify:
+            self.handle_bad_download()
+        return candidate_verify
 
     def download(self):
         try:
@@ -112,6 +116,27 @@ def save(self, r):
                 print('>', end='')
                 sys.stdout.flush()
 
+    def handle_bad_download(self):
+        if os.path.exists(self.filename):
+            # rename file for further investigation
+            try:
+                # NB: using `self.sha_actual` may create unbounded number of files
+                rename_target = self.filename + '.invalid'
+                # TODO: use os.replace (Python 3.3+)
+                try:
+                    if os.path.exists(rename_target):  # avoid FileExistsError on Windows from os.rename()
+                        os.remove(rename_target)
+                finally:
+                    os.rename(self.filename, rename_target)
+                    print('  renaming invalid file to ' + rename_target)
+            except:
+                import traceback
+                traceback.print_exc()
+            finally:
+                if os.path.exists(self.filename):
+                    print('  deleting invalid file')
+                    os.remove(self.filename)
+
 
 def GDrive(gid):
     def download_gdrive(dst):