diff --git a/.test-conda-env-py3.yml b/.test-conda-env-py3.yml
index b2b8b1b47c08a0c809a666abce034ade305e1278..2b80ce7eb2427b3114108522cd3d9a136b509239 100644
--- a/.test-conda-env-py3.yml
+++ b/.test-conda-env-py3.yml
@@ -13,4 +13,5 @@ dependencies:
 - python=3.5
 - symengine=0.3.0
 - python-symengine=0.3.0
+- mpfr
 # things not in here: loopy boxtree pymbolic pyfmmlib