diff --git a/README.md b/README.md
index a262ce28..8638a1a7 100644
--- a/README.md
+++ b/README.md
@@ -23,6 +23,8 @@ Please review our [roadmap](https://github.com/material-table-core/core/wiki/Roa
 
 </div>
 
+# Mui V6 is currently in progress
+
 # Sponsoring
 
 We are now able to be sponsored via [Github Sponsors](https://github.com/sponsors/material-table-core?o=esb) or [Open collective](https://opencollective.com/material-table-core)!
diff --git a/src/components/MTableAction/index.js b/src/components/MTableAction/index.js
index b97dcda4..0a78f47d 100644
--- a/src/components/MTableAction/index.js
+++ b/src/components/MTableAction/index.js
@@ -80,7 +80,7 @@ function MTableAction({
   if (action.tooltip) {
     // fix for issue #1049
     // https://github.com/mbrn/material-table/issues/1049
-    return disabled ? (
+    return isDisabled ? (
       <Tooltip title={action.tooltip}>
         <span>{button}</span>
       </Tooltip>
@@ -99,12 +99,13 @@ const defaultProps = {
 
 MTableAction.propTypes = {
   action: PropTypes.oneOfType([PropTypes.func, PropTypes.object]).isRequired,
+  columns: PropTypes.array,
   data: PropTypes.oneOfType([
     PropTypes.object,
     PropTypes.arrayOf(PropTypes.object)
   ]),
   disabled: PropTypes.bool,
-  onColumnsChanged: PropTypes.func.isRequired,
+  onColumnsChanged: PropTypes.func,
   size: PropTypes.string
 };
 
diff --git a/src/components/MTableActions/index.js b/src/components/MTableActions/index.js
index 08c7f30a..821c97bb 100644
--- a/src/components/MTableActions/index.js
+++ b/src/components/MTableActions/index.js
@@ -32,6 +32,7 @@ function MTableActions({
 }
 
 MTableActions.propTypes = {
+  columns: PropTypes.array,
   components: PropTypes.object.isRequired,
   actions: PropTypes.array.isRequired,
   data: PropTypes.oneOfType([
@@ -39,6 +40,7 @@ MTableActions.propTypes = {
     PropTypes.arrayOf(PropTypes.object)
   ]),
   disabled: PropTypes.bool,
+  onColumnsChanged: PropTypes.func,
   size: PropTypes.string,
   forwardedRef: PropTypes.element
 };
diff --git a/src/utils/data-manager.js b/src/utils/data-manager.js
index 28816a02..8e394228 100644
--- a/src/utils/data-manager.js
+++ b/src/utils/data-manager.js
@@ -1110,14 +1110,20 @@ export default class DataManager {
 
           if (!group) {
             const path = [...(o.path || []), value];
+            let isDefaultExpanded = false;
+            switch (typeof this.defaultExpanded) {
+              case 'boolean':
+                isDefaultExpanded = this.defaultExpanded;
+                break;
+              case 'function':
+                isDefaultExpanded = this.defaultExpanded(currentRow);
+                break;
+            }
             const oldGroup = this.findGroupByGroupPath(
               this.groupedData,
               path
             ) || {
-              isExpanded:
-                typeof this.defaultExpanded === 'boolean'
-                  ? this.defaultExpanded
-                  : false
+              isExpanded: isDefaultExpanded
             };
 
             group = {
@@ -1227,10 +1233,15 @@ export default class DataManager {
         !this.columns.some((columnDef) => columnDef.tableData.filterValue)
       ) {
         if (rowData.tableData.isTreeExpanded === undefined) {
-          const isExpanded =
-            typeof this.defaultExpanded === 'boolean'
-              ? this.defaultExpanded
-              : this.defaultExpanded(rowData);
+          let isExpanded = false;
+          switch (typeof this.defaultExpanded) {
+            case 'boolean':
+              isDefaultExpanded = this.defaultExpanded;
+              break;
+            case 'function':
+              isDefaultExpanded = this.defaultExpanded(rowData);
+              break;
+          }
           rowData.tableData.isTreeExpanded = isExpanded;
         }
       }