diff --git a/packages/core/src/collectionApi/delete.js b/packages/core/src/collectionApi/delete.js
index b93b65b0a9..897c199c46 100644
--- a/packages/core/src/collectionApi/delete.js
+++ b/packages/core/src/collectionApi/delete.js
@@ -3,6 +3,8 @@ import { _deleteRecord } from "../recordApi/delete"
 import { getAllIdsIterator } from "../indexing/allIds"
 import { permission } from "../authApi/permissions"
 import { getCollectionDir } from "../recordApi/recordInfo"
+import { ensureCollectionIsInitialised } from "./initialise"
+import { getNodeForCollectionPath } from "../templateApi/hierarchy"
 
 export const deleteCollection = (app, disableCleanup = false) => async key =>
   apiWrapper(
@@ -25,14 +27,19 @@ export const _deleteCollection = async (app, key, disableCleanup) => {
   key = safeKey(key)
   const collectionDir = getCollectionDir(app.hierarchy, key)
   await deleteRecords(app, key)
-  await deleteCollectionFolder(app, collectionDir)
+  await deleteCollectionFolder(app, key, collectionDir)
   if (!disableCleanup) {
     await app.cleanupTransactions()
   }
 }
 
-const deleteCollectionFolder = async (app, dir) =>
+const deleteCollectionFolder = async (app, key, dir) => {
   await app.datastore.deleteFolder(dir)
+  await ensureCollectionIsInitialised(
+    app.datastore,
+    getNodeForCollectionPath(app.hierarchy)(key),
+    dir)
+}
 
 const deleteRecords = async (app, key) => {
   const iterate = await getAllIdsIterator(app)(key)
diff --git a/packages/core/src/collectionApi/initialise.js b/packages/core/src/collectionApi/initialise.js
index 8190c58db8..3aac1c2889 100644
--- a/packages/core/src/collectionApi/initialise.js
+++ b/packages/core/src/collectionApi/initialise.js
@@ -6,7 +6,7 @@ import {
 } from "../templateApi/hierarchy"
 import { $, allTrue, joinKey } from "../common"
 
-const ensureCollectionIsInitialised = async (datastore, node, dir) => {
+export const ensureCollectionIsInitialised = async (datastore, node, dir) => {
   if (!(await datastore.exists(dir))) {
     await datastore.createFolder(dir)
     await datastore.createFolder(joinKey(dir, node.nodeId))
diff --git a/packages/core/test/collectionApi.delete.spec.js b/packages/core/test/collectionApi.delete.spec.js
index 09bddb8ef2..8841cbc051 100644
--- a/packages/core/test/collectionApi.delete.spec.js
+++ b/packages/core/test/collectionApi.delete.spec.js
@@ -8,7 +8,7 @@ import { permission } from "../src/authApi/permissions"
 
 describe("collectionApi > delete", () => {
   it("should remove every key in collection's path", async () => {
-    const { recordApi, collectionApi } = await setupApphierarchy(
+    const { recordApi, collectionApi, appHierarchy } = await setupApphierarchy(
       basicAppHierarchyCreator_WithFields
     )
     const record1 = recordApi.getNew("/customers", "customer")
@@ -31,7 +31,10 @@ describe("collectionApi > delete", () => {
       filter(k => splitKey(k)[0] === "customers"),
     ])
 
-    expect(remainingKeys).toEqual([])
+    expect(remainingKeys).toEqual([
+      "/customers",
+      `/customers/${appHierarchy.customerRecord.nodeId}`,
+    ])
   })
 
   it("should not delete anything that is not in its path", async () => {
@@ -51,7 +54,8 @@ describe("collectionApi > delete", () => {
       filter(k => splitKey(k)[0] === "customers"),
     ])
 
-    const expectedRemainingKeys = allKeys.length - customerKeys.length
+    const expectedRemainingKeys = allKeys.length - customerKeys.length + 2
+    // +2 because is should keep the collection folders: /customers & /customers/1
 
     await collectionApi.delete("/customers")
 
diff --git a/packages/server/middleware/routeHandlers/upgradeData.js b/packages/server/middleware/routeHandlers/upgradeData.js
index 24026ace66..a9f2fcf349 100644
--- a/packages/server/middleware/routeHandlers/upgradeData.js
+++ b/packages/server/middleware/routeHandlers/upgradeData.js
@@ -6,5 +6,6 @@ module.exports = async ctx => {
   accessLevels.version = existingAccessLevels.version
   await ctx.instance.authApi.saveAccessLevels(accessLevels)
   await ctx.instance.templateApi.upgradeData(ctx.request.body.newHierarchy)
+  await ctx.master.clearAllSessions(ctx.params.appname)
   ctx.response.status = StatusCodes.OK
 }
diff --git a/packages/server/utilities/masterAppInternal.js b/packages/server/utilities/masterAppInternal.js
index e02862f61c..3cb358434e 100644
--- a/packages/server/utilities/masterAppInternal.js
+++ b/packages/server/utilities/masterAppInternal.js
@@ -325,6 +325,15 @@ module.exports = async context => {
     }
   }
 
+  const clearAllSessions = async appname => {
+    if (isMaster(appname)) {
+      await bb.collectionApi.delete("/mastersessions")
+    } else {
+      const app = await getApplication(appname)
+      await bb.collectionApi.delete(`/applications/${app.id}/sessions`)
+    }
+  }
+
   const getApplicationWithInstances = async appname => {
     const app = cloneDeep(await getApplication(appname))
     app.instances = await bb.indexApi.listItems(
@@ -346,7 +355,7 @@ module.exports = async context => {
     await bb.recordApi.save(userInMaster)
   }
 
-  const deleteLatestPackageFromCache = (appname) => {
+  const deleteLatestPackageFromCache = appname => {
     deleteCachedPackage(context, appname, LATEST_VERSIONID)
   }
 
@@ -370,5 +379,6 @@ module.exports = async context => {
     getFullAccessApiForMaster,
     getApplicationWithInstances,
     deleteLatestPackageFromCache,
+    clearAllSessions,
   }
 }