diff --git a/requirements.txt b/requirements.txt
index eb9d65e..f622fda 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,6 +6,7 @@ landlab>=2
 matplotlib
 model_metadata<0.8
 netcdf4
+numpy<2  # see #173
 pyyaml
 scipy
 shapely