diff --git a/requirements.txt b/requirements.txt
index 6ee5dff9..26173852 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 absl-py
 cirq-core~=1.0
-numpy~=1.21
+numpy~=1.16
 pybind11
 typing_extensions