diff --git a/requests/utils.py b/requests/utils.py
index 3b43ad7d..227f7c4b 100644
--- a/requests/utils.py
+++ b/requests/utils.py
@@ -86,17 +86,17 @@ def super_len(o):
             # let requests chunk it instead.
             if total_length is not None:
                 current_position = total_length
+        else:
+            if hasattr(o, 'seek') and total_length is None:
+                # StringIO and BytesIO have seek but no useable fileno
 
-        if hasattr(o, 'seek') and total_length is None:
-            # StringIO and BytesIO have seek but no useable fileno
+                # seek to end of file
+                o.seek(0, 2)
+                total_length = o.tell()
 
-            # seek to end of file
-            o.seek(0, 2)
-            total_length = o.tell()
-
-            # seek back to current position to support
-            # partially read file-like objects
-            o.seek(current_position or 0)
+                # seek back to current position to support
+                # partially read file-like objects
+                o.seek(current_position or 0)
 
     if total_length is None:
         total_length = 0
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 7e0b4f28..9fd0bcf4 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -51,6 +51,18 @@ class TestSuperLen:
 
         assert super_len(BoomFile()) == 0
 
+    @pytest.mark.parametrize('error', [IOError, OSError])
+    def test_super_len_tell_ioerror(self, error):
+        """Ensure that if tell gives an IOError super_len doesn't fail"""
+        class NoLenBoomFile(object):
+            def tell(self):
+                raise error()
+
+            def seek(self, offset, whence):
+                pass
+
+        assert super_len(NoLenBoomFile()) == 0
+
     def test_string(self):
         assert super_len('Test') == 4