diff --git a/setup.py b/setup.py
index d6ebc46a385eb46e1b26c8614483ccad0444f2fd..915b72e621e733aa5536fdc8ece815a18dcd0785 100644
--- a/setup.py
+++ b/setup.py
@@ -30,7 +30,7 @@ def check_version(installed_binary_c_version, required_binary_c_version):
     assert installed_binary_c_version == required_binary_c_version, message
 
 ###
-REQUIRED_BINARY_C_VERSION = '2.1.7'
+REQUIRED_BINARY_C_VERSION = '2.1.6'
 
 ####
 GSL_DIR = os.getenv("GSL_DIR", None)