diff --git a/setup.py b/setup.py
index <HASH>..<HASH> 100755
--- a/setup.py
+++ b/setup.py
@@ -11,7 +11,12 @@ import sys
 
 from distutils.core import setup
 from distutils.extension import Extension
-from Cython.Distutils import build_ext
+
+try:
+    from Cython.Distutils import build_ext
+except ImportError:
+    # Fallback to plain-old ``distutils`` for RTFD builds.
+    from distutils.command import build_ext
 
 
 DISTNAME = "hmmlearn"
MAINT bypass Cython for RTFD builds