diff --git a/Lib/test/test_textwrap.py b/Lib/test/test_textwrap.py
index 904c79091dd..a0111680b42 100644
--- a/Lib/test/test_textwrap.py
+++ b/Lib/test/test_textwrap.py
@@ -305,6 +305,16 @@ How *do* you spell that odd word, anyways?
                         ['Did you say "supercalifragilisticexpialidocious?"',
                          'How *do* you spell that odd word, anyways?'])
 
+        # SF bug 797650.  Prevent an infinite loop by making sure that at
+        # least one character gets split off on every pass.
+        self.check_wrap('-'*10+'hello', 10,
+                        ['----------',
+                         '               h',
+                         '               e',
+                         '               l',
+                         '               l',
+                         '               o'],
+                        subsequent_indent = ' '*15)
 
     def test_nobreak_long(self):
         # Test with break_long_words disabled
diff --git a/Lib/textwrap.py b/Lib/textwrap.py
index a4a549848f3..f371fbbe5ac 100644
--- a/Lib/textwrap.py
+++ b/Lib/textwrap.py
@@ -168,7 +168,7 @@ class TextWrapper:
         Handle a chunk of text (most likely a word, not whitespace) that
         is too long to fit in any line.
         """
-        space_left = width - cur_len
+        space_left = max(width - cur_len, 1)
 
         # If we're allowed to break long words, then do so: put as much
         # of the next chunk onto the current line as will fit.