diff --git a/projects/igniteui-angular/src/lib/directives/for-of/for_of.directive.spec.ts b/projects/igniteui-angular/src/lib/directives/for-of/for_of.directive.spec.ts
index a78def1ec2f..92cdaf4be87 100644
--- a/projects/igniteui-angular/src/lib/directives/for-of/for_of.directive.spec.ts
+++ b/projects/igniteui-angular/src/lib/directives/for-of/for_of.directive.spec.ts
@@ -255,6 +255,19 @@ describe('IgxForOf directive -', () => {
             }
         });
 
+        it('should not throw error when itemSize is changed while data is null/undefined.', () => {
+            let errorMessage = '';
+            fix.componentInstance.data = null;
+            fix.detectChanges();
+            try {
+                fix.componentInstance.itemSize = '100px';
+                fix.detectChanges();
+            } catch (ex) {
+                errorMessage = ex.message;
+            }
+            expect(errorMessage).toBe('');
+        });
+
         it('should allow initially undefined value for igxForOf and then detect changes correctly once the value is updated', async () => {
             fix = TestBed.createComponent(VerticalVirtualNoDataComponent);
             expect(() => {
diff --git a/projects/igniteui-angular/src/lib/directives/for-of/for_of.directive.ts b/projects/igniteui-angular/src/lib/directives/for-of/for_of.directive.ts
index 1971d1e72bb..8115f7a49a1 100644
--- a/projects/igniteui-angular/src/lib/directives/for-of/for_of.directive.ts
+++ b/projects/igniteui-angular/src/lib/directives/for-of/for_of.directive.ts
@@ -423,7 +423,8 @@ export class IgxForOfDirective<T> implements OnInit, OnChanges, DoCheck, OnDestr
             }
         }
         const defaultItemSize = 'igxForItemSize';
-        if (defaultItemSize in changes && !changes[defaultItemSize].firstChange && this.igxForScrollOrientation === 'vertical') {
+        if (defaultItemSize in changes && !changes[defaultItemSize].firstChange &&
+            this.igxForScrollOrientation === 'vertical' && this.igxForOf) {
             // handle default item size changed.
             this.initSizesCache(this.igxForOf);
             this._applyChanges();
@@ -1325,7 +1326,8 @@ export class IgxGridForOfDirective<T> extends IgxForOfDirective<T> implements On
             }
         }
         const defaultItemSize = 'igxForItemSize';
-        if (defaultItemSize in changes && !changes[defaultItemSize].firstChange && this.igxForScrollOrientation === 'vertical') {
+        if (defaultItemSize in changes && !changes[defaultItemSize].firstChange &&
+             this.igxForScrollOrientation === 'vertical' && this.igxForOf) {
             // handle default item size changed.
             this.initSizesCache(this.igxForOf);
         }
diff --git a/src/app/hierarchical-grid-remote/hierarchical-grid-remote.sample.html b/src/app/hierarchical-grid-remote/hierarchical-grid-remote.sample.html
index 7882095dd70..1835cc644c7 100644
--- a/src/app/hierarchical-grid-remote/hierarchical-grid-remote.sample.html
+++ b/src/app/hierarchical-grid-remote/hierarchical-grid-remote.sample.html
@@ -1,6 +1,6 @@
 <button (click)='setterBindingChange()'>Set rowSelectable via binding</button>
 <button (click)='setterChange()'>Set rowSelectable via setter on 1st row island</button>
-<igx-hierarchical-grid #grid1 [data]="remoteData" [primaryKey]="'CustomerID'" [autoGenerate]="false" [height]="'800px'" [width]="'100%'" #hGrid [emptyGridMessage]="''">
+<igx-hierarchical-grid #grid1  displayDensity="cosy" [data]="remoteData" [primaryKey]="'CustomerID'" [autoGenerate]="false" [height]="'800px'" [width]="'100%'" #hGrid [emptyGridMessage]="''">
     <igx-column field="CustomerID"></igx-column>
     <igx-column field="CompanyName"></igx-column>
     <igx-column field="ContactName"></igx-column>