diff --git a/Dockerfile-prep b/Dockerfile-prep
index 786ea90..5e0e626 100644
--- a/Dockerfile-prep
+++ b/Dockerfile-prep
@@ -19,7 +19,8 @@ WORKDIR ${HOME}
 RUN pip install scikit-learn==1.2.2\
   pdb2pqr==3.6.1\
   im-standardize-molecule==0.1.0\
-  im-data-manager-job-utilities==1.1.1
+  im-data-manager-job-utilities==1.1.1\
+  sigfig==1.3.19
 
 COPY *.py fpscores.pkl.gz site_substructures.smarts ./
 COPY moldb/* ./moldb/