diff --git a/setup.py b/setup.py
index 30ee0575..d4a572a5 100644
--- a/setup.py
+++ b/setup.py
@@ -93,8 +93,12 @@ def default_environment():
         if (len(a.targets) == 1 and
                 isinstance(a.targets[0], ast.Name) and
                 a.targets[0].id == "__version__" and
-                isinstance(a.value, ast.Str)):
-            version = a.value.s
+                (
+                    (hasattr(ast, "Str") and isinstance(a.value, ast.Str)) or
+                    (isinstance(a.value, ast.Constant) and isinstance(a.value.value, str))
+                )
+                ):
+            version = getattr(a.value, "s", a.value.value)
 
 setup(name='html5lib',
       version=version,