diff --git a/.circleci/config.yml b/.circleci/config.yml
index ec3848b048..5395028426 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -23,99 +23,106 @@ jobs:
       - run: docker push matrixdotorg/synapse:latest
       - run: docker push matrixdotorg/synapse:latest-py3
   sytestpy2:
-    machine: true
+    docker:
+      - image: matrixdotorg/sytest-synapsepy2
+    working_directory: /src
     steps:
       - checkout
-      - run: docker pull matrixdotorg/sytest-synapsepy2
-      - run: docker run --rm -it -v $(pwd)\:/src -v $(pwd)/logs\:/logs matrixdotorg/sytest-synapsepy2
+      - run: /synapse_sytest.sh
       - store_artifacts:
-          path: ~/project/logs
+          path: /logs
           destination: logs
       - store_test_results:
-          path: logs
+          path: /logs
   sytestpy2postgres:
-    machine: true
+    docker:
+      - image: matrixdotorg/sytest-synapsepy2
+    working_directory: /src
     steps:
       - checkout
-      - run: docker pull matrixdotorg/sytest-synapsepy2
-      - run: docker run --rm -it -v $(pwd)\:/src -v $(pwd)/logs\:/logs -e POSTGRES=1 matrixdotorg/sytest-synapsepy2
+      - run: POSTGRES=1 /synapse_sytest.sh
       - store_artifacts:
-          path: ~/project/logs
+          path: /logs
           destination: logs
       - store_test_results:
-          path: logs
+          path: /logs
   sytestpy2merged:
-    machine: true
+    docker:
+      - image: matrixdotorg/sytest-synapsepy2
+    working_directory: /src
     steps:
       - checkout
       - run: bash .circleci/merge_base_branch.sh
-      - run: docker pull matrixdotorg/sytest-synapsepy2
-      - run: docker run --rm -it -v $(pwd)\:/src -v $(pwd)/logs\:/logs matrixdotorg/sytest-synapsepy2
+      - run: /synapse_sytest.sh
       - store_artifacts:
-          path: ~/project/logs
+          path: /logs
           destination: logs
       - store_test_results:
-          path: logs
-
+          path: /logs
   sytestpy2postgresmerged:
-    machine: true
+    docker:
+      - image: matrixdotorg/sytest-synapsepy2
+    working_directory: /src
     steps:
       - checkout
       - run: bash .circleci/merge_base_branch.sh
-      - run: docker pull matrixdotorg/sytest-synapsepy2
-      - run: docker run --rm -it -v $(pwd)\:/src -v $(pwd)/logs\:/logs -e POSTGRES=1 matrixdotorg/sytest-synapsepy2
+      - run: POSTGRES=1 /synapse_sytest.sh
       - store_artifacts:
-          path: ~/project/logs
+          path: /logs
           destination: logs
       - store_test_results:
-          path: logs
+          path: /logs
 
   sytestpy3:
-    machine: true
+    docker:
+      - image: matrixdotorg/sytest-synapsepy3
+    working_directory: /src
     steps:
       - checkout
-      - run: docker pull matrixdotorg/sytest-synapsepy3
-      - run: docker run --rm -it -v $(pwd)\:/src -v $(pwd)/logs\:/logs matrixdotorg/sytest-synapsepy3
+      - run: /synapse_sytest.sh
       - store_artifacts:
-          path: ~/project/logs
+          path: /logs
           destination: logs
       - store_test_results:
-          path: logs
+          path: /logs
   sytestpy3postgres:
-    machine: true
+    docker:
+      - image: matrixdotorg/sytest-synapsepy3
+    working_directory: /src
     steps:
       - checkout
-      - run: docker pull matrixdotorg/sytest-synapsepy3
-      - run: docker run --rm -it -v $(pwd)\:/src -v $(pwd)/logs\:/logs -e POSTGRES=1 matrixdotorg/sytest-synapsepy3
+      - run: POSTGRES=1 /synapse_sytest.sh
       - store_artifacts:
-          path: ~/project/logs
+          path: /logs
           destination: logs
       - store_test_results:
-          path: logs
+          path: /logs
   sytestpy3merged:
-    machine: true
+    docker:
+      - image: matrixdotorg/sytest-synapsepy3
+    working_directory: /src
     steps:
       - checkout
       - run: bash .circleci/merge_base_branch.sh
-      - run: docker pull matrixdotorg/sytest-synapsepy3
-      - run: docker run --rm -it -v $(pwd)\:/src -v $(pwd)/logs\:/logs matrixdotorg/sytest-synapsepy3
+      - run: /synapse_sytest.sh
       - store_artifacts:
-          path: ~/project/logs
+          path: /logs
           destination: logs
       - store_test_results:
-          path: logs
+          path: /logs
   sytestpy3postgresmerged:
-    machine: true
+    docker:
+      - image: matrixdotorg/sytest-synapsepy3
+    working_directory: /src
     steps:
       - checkout
       - run: bash .circleci/merge_base_branch.sh
-      - run: docker pull matrixdotorg/sytest-synapsepy3
-      - run: docker run --rm -it -v $(pwd)\:/src -v $(pwd)/logs\:/logs -e POSTGRES=1 matrixdotorg/sytest-synapsepy3
+      - run: POSTGRES=1 /synapse_sytest.sh
       - store_artifacts:
-          path: ~/project/logs
+          path: /logs
           destination: logs
       - store_test_results:
-          path: logs
+          path: /logs
 
 workflows:
   version: 2
diff --git a/.circleci/merge_base_branch.sh b/.circleci/merge_base_branch.sh
index 6b0bf3aa48..b2c8c40f4c 100755
--- a/.circleci/merge_base_branch.sh
+++ b/.circleci/merge_base_branch.sh
@@ -16,7 +16,7 @@ then
     GITBASE="develop"
 else
     # Get the reference, using the GitHub API
-    GITBASE=`curl -q https://api.github.com/repos/matrix-org/synapse/pulls/${CIRCLE_PR_NUMBER} | jq -r '.base.ref'`
+    GITBASE=`wget -O- https://api.github.com/repos/matrix-org/synapse/pulls/${CIRCLE_PR_NUMBER} | jq -r '.base.ref'`
 fi
 
 # Show what we are before
@@ -31,4 +31,4 @@ git fetch -u origin $GITBASE
 git merge --no-edit origin/$GITBASE
 
 # Show what we are after.
-git show -s
\ No newline at end of file
+git show -s
diff --git a/changelog.d/4041.misc b/changelog.d/4041.misc
new file mode 100644
index 0000000000..8cce9daac9
--- /dev/null
+++ b/changelog.d/4041.misc
@@ -0,0 +1 @@
+Run the CircleCI builds in docker containers