diff --git a/metagraph/workflows/requirements.txt b/metagraph/workflows/requirements.txt
index e5d072a3b1..63da3d7a81 100644
--- a/metagraph/workflows/requirements.txt
+++ b/metagraph/workflows/requirements.txt
@@ -1,2 +1,3 @@
 snakemake>=5
+pulp==2.7.0
 pandas