diff --git a/dockerfiles/alpine/Dockerfile b/dockerfiles/alpine/Dockerfile
index ab67201..b074e10 100644
--- a/dockerfiles/alpine/Dockerfile
+++ b/dockerfiles/alpine/Dockerfile
@@ -17,7 +17,14 @@ RUN apk add --update \
     jq \
     openssh \
     tar \
-    mercurial
+    python2 \
+    python2-dev \
+    py2-pip \
+    build-base
+
+RUN pip2 install mercurial
+RUN pip2 install hg-evolve
+
 COPY --from=builder /assets /opt/resource
 ADD assets/askpass.sh /opt/resource
 RUN chmod +x /opt/resource/*
diff --git a/dockerfiles/ubuntu/Dockerfile b/dockerfiles/ubuntu/Dockerfile
index 588e943..ce061b4 100644
--- a/dockerfiles/ubuntu/Dockerfile
+++ b/dockerfiles/ubuntu/Dockerfile
@@ -15,8 +15,16 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
       gnupg \
       jq \
       openssh-client \
-      mercurial \
-    && rm -rf /var/lib/apt/lists/*
+      python \
+      python-pip \
+      build-essential \
+      python-all-dev \
+      python-setuptools \
+      python-wheel \
+    && rm -rf /var/lib/apt/lists/* \
+    && pip2 install mercurial \
+    && pip2 install hg-evolve
+
 COPY --from=builder /assets /opt/resource
 ADD assets/askpass.sh /opt/resource
 RUN chmod +x /opt/resource/*
diff --git a/hgrc b/hgrc
index d2d45ca..0d3599f 100644
--- a/hgrc
+++ b/hgrc
@@ -3,3 +3,6 @@ username = User Name <user@example.com>
 
 [phases]
 publish = false
+
+[extensions]
+evolve =
\ No newline at end of file
diff --git a/test/test_in.sh b/test/test_in.sh
index 8503a1a..fd27269 100755
--- a/test/test_in.sh
+++ b/test/test_in.sh
@@ -162,6 +162,35 @@ test_it_can_get_with_ssl_cert_checks_disabled() {
   sleep 0.1
 }
 
+test_it_ignores_obsolete() {
+  local repo=$(init_repo)
+  local ref1=$(make_commit $repo)
+  local ref2=$(make_commit $repo)
+
+  local dest=$TMPDIR/destination
+
+  local expected1=$(echo "{\"ref\": $(echo $ref2 | jq -R .)}" | jq ".")
+  assertEquals "$expected1" "$(get_uri $repo $dest | jq '.version')"
+
+  if [ ! -e "$dest/some-file" ]; then
+    fail "expected some-file to exist in the working directory"
+  fi
+  assertEquals "$ref2" "$(get_working_dir_ref $dest)"
+
+  rm -rf $dest
+
+  # prune $ref2 and verify that concourse sees $ref1 as the tip
+  hg prune --cwd $repo $ref2
+
+  local expected2=$(echo "{\"ref\": $(echo $ref1 | jq -R .)}" | jq ".")
+  assertEquals "$expected2" "$(get_uri $repo $dest | jq '.version')"
+
+  if [ ! -e "$dest/some-file" ]; then
+    fail "expected some-file to exist in the working directory"
+  fi
+  assertEquals "$ref1" "$(get_working_dir_ref $dest)"
+}
+
 test_path_changed() {
   local repo1=$(init_repo)
   local repo1_ref=$(make_commit $repo1)