diff --git a/images/docker/api/Dockerfile b/images/docker/api/Dockerfile
index bc7b88f7a..b71ae38f4 100644
--- a/images/docker/api/Dockerfile
+++ b/images/docker/api/Dockerfile
@@ -1,6 +1,6 @@
 FROM docker/whalesay:latest
 
-RUN sudo apt-get update && sudo apt-get install -y build-essential python-pip git-core python-dev libssl-dev libffi-dev rng-tools libgmp3-dev
+RUN sudo apt-get update && sudo apt-get install -y build-essential python-pip git-core python-dev libssl-dev libffi-dev rng-tools libgmp3-dev lsof
 RUN sudo pip install pip --upgrade
 RUN sudo pip install blockstack --upgrade
 
diff --git a/images/docker/testmode/Dockerfile b/images/docker/testmode/Dockerfile
index e7c339595..92e187d7b 100644
--- a/images/docker/testmode/Dockerfile
+++ b/images/docker/testmode/Dockerfile
@@ -1,7 +1,7 @@
 FROM docker/whalesay:latest
 
 # Install Blockstack Core
-RUN sudo apt-get update && sudo apt-get install -y build-essential python-pip git-core python-dev libssl-dev libffi-dev rng-tools libgmp3-dev
+RUN sudo apt-get update && sudo apt-get install -y build-essential python-pip git-core python-dev libssl-dev libffi-dev rng-tools libgmp3-dev lsof
 RUN sudo pip install pip --upgrade
 RUN sudo pip install blockstack --upgrade