diff --git a/setup.py b/setup.py
index 200e6f6..798b9fa 100644
--- a/setup.py
+++ b/setup.py
@@ -15,7 +15,7 @@ CFLAGS = ['-O2']
 
 ROOT = pathlib.Path(__file__).parent
 
-CYTHON_DEPENDENCY = 'Cython(>=0.29.24,<0.30.0)'
+CYTHON_DEPENDENCY = 'Cython(>=0.29.24,<4)'
 
 
 class httptools_build_ext(build_ext):
