diff --git a/packages/@glimmer/integration-tests/lib/suites/in-element.ts b/packages/@glimmer/integration-tests/lib/suites/in-element.ts
index d38119ff1..960377f7d 100644
--- a/packages/@glimmer/integration-tests/lib/suites/in-element.ts
+++ b/packages/@glimmer/integration-tests/lib/suites/in-element.ts
@@ -29,6 +29,29 @@ export class InElementSuite extends RenderTest {
     this.assertStableNodes();
   }
 
+  @test
+  'clears existing content'() {
+    let externalElement = this.delegate.createElement('div');
+    let initialContent = '<p>Hello there!</p>';
+    replaceHTML(externalElement, initialContent);
+
+    this.render('{{#in-element externalElement}}[{{foo}}]{{/in-element}}', {
+      externalElement,
+      foo: 'Yippie!',
+    });
+
+    equalsElement(externalElement, 'div', {}, '[Yippie!]');
+    this.assertStableRerender();
+
+    this.rerender({ foo: 'Double Yups!' });
+    equalsElement(externalElement, 'div', {}, '[Double Yups!]');
+    this.assertStableNodes();
+
+    this.rerender({ foo: 'Yippie!' });
+    equalsElement(externalElement, 'div', {}, '[Yippie!]');
+    this.assertStableNodes();
+  }
+
   @test
   'Changing to falsey'() {
     let first = this.delegate.createElement('div');
@@ -79,10 +102,13 @@ export class InElementSuite extends RenderTest {
     let initialContent = '<p>Hello there!</p>';
     replaceHTML(externalElement, initialContent);
 
-    this.render(stripTight`{{#in-element externalElement}}[{{foo}}]{{/in-element}}`, {
-      externalElement,
-      foo: 'Yippie!',
-    });
+    this.render(
+      stripTight`{{#in-element externalElement insertBefore=null}}[{{foo}}]{{/in-element}}`,
+      {
+        externalElement,
+        foo: 'Yippie!',
+      }
+    );
 
     equalsElement(externalElement, 'div', {}, `${initialContent}[Yippie!]`);
     this.assertHTML('<!---->');
@@ -105,38 +131,17 @@ export class InElementSuite extends RenderTest {
   }
 
   @test
-  'With nextSibling'() {
+  '`insertBefore` can only be null'() {
     let externalElement = this.delegate.createElement('div');
-    replaceHTML(externalElement, '<b>Hello</b><em>there!</em>');
-
-    this.render(
-      stripTight`{{#in-element externalElement nextSibling=nextSibling}}[{{foo}}]{{/in-element}}`,
-      { externalElement, nextSibling: externalElement.lastChild, foo: 'Yippie!' }
-    );
-
-    equalsElement(externalElement, 'div', {}, '<b>Hello</b>[Yippie!]<em>there!</em>');
-    this.assertHTML('<!---->');
-    this.assertStableRerender();
-
-    this.rerender({ foo: 'Double Yips!' });
-    equalsElement(externalElement, 'div', {}, '<b>Hello</b>[Double Yips!]<em>there!</em>');
-    this.assertHTML('<!---->');
-    this.assertStableNodes();
+    let before = this.delegate.createElement('div');
 
-    this.rerender({ nextSibling: null });
-    equalsElement(externalElement, 'div', {}, '<b>Hello</b><em>there!</em>[Double Yips!]');
-    this.assertHTML('<!---->');
-    this.assertStableRerender();
-
-    this.rerender({ externalElement: null });
-    equalsElement(externalElement, 'div', {}, '<b>Hello</b><em>there!</em>');
-    this.assertHTML('<!---->');
-    this.assertStableRerender();
-
-    this.rerender({ externalElement, nextSibling: externalElement.lastChild, foo: 'Yippie!' });
-    equalsElement(externalElement, 'div', {}, '<b>Hello</b>[Yippie!]<em>there!</em>');
-    this.assertHTML('<!---->');
-    this.assertStableRerender();
+    this.assert.throws(() => {
+      this.render('{{#in-element externalElement insertBefore=before}}[{{foo}}]{{/in-element}}', {
+        externalElement,
+        before,
+        foo: 'Yippie!',
+      });
+    }, /insertBefore only takes `null` as an argument/);
   }
 
   @test
diff --git a/packages/@glimmer/interfaces/lib/dom/attributes.d.ts b/packages/@glimmer/interfaces/lib/dom/attributes.d.ts
index 69f70986e..ed526446e 100644
--- a/packages/@glimmer/interfaces/lib/dom/attributes.d.ts
+++ b/packages/@glimmer/interfaces/lib/dom/attributes.d.ts
@@ -40,7 +40,7 @@ export interface DOMStack {
   pushRemoteElement(
     element: SimpleElement,
     guid: string,
-    nextSibling: Option<SimpleNode>
+    insertBefore: Option<null>
   ): Option<RemoteLiveBlock>;
   popRemoteElement(): void;
   popElement(): void;
diff --git a/packages/@glimmer/node/lib/serialize-builder.ts b/packages/@glimmer/node/lib/serialize-builder.ts
index 9e83bc848..b845d1530 100644
--- a/packages/@glimmer/node/lib/serialize-builder.ts
+++ b/packages/@glimmer/node/lib/serialize-builder.ts
@@ -96,13 +96,13 @@ class SerializeBuilder extends NewElementBuilder implements ElementBuilder {
   pushRemoteElement(
     element: SimpleElement,
     cursorId: string,
-    nextSibling: Option<SimpleNode> = null
+    insertBefore: Option<null> = null
   ): Option<RemoteLiveBlock> {
     let { dom } = this;
     let script = dom.createElement('script');
     script.setAttribute('glmr', cursorId);
-    dom.insertBefore(element, script, nextSibling);
-    return super.pushRemoteElement(element, cursorId, nextSibling);
+    dom.insertBefore(element, script, insertBefore);
+    return super.pushRemoteElement(element, cursorId, insertBefore);
   }
 }
 
diff --git a/packages/@glimmer/opcode-compiler/lib/syntax/builtins.ts b/packages/@glimmer/opcode-compiler/lib/syntax/builtins.ts
index c90ef1dd4..cf6b1e51b 100644
--- a/packages/@glimmer/opcode-compiler/lib/syntax/builtins.ts
+++ b/packages/@glimmer/opcode-compiler/lib/syntax/builtins.ts
@@ -173,7 +173,7 @@ export function populateBuiltins(
 
         for (let i = 0; i < keys.length; i++) {
           let key = keys[i];
-          if (key === 'nextSibling' || key === 'guid') {
+          if (key === 'guid' || key === 'insertBefore') {
             actions.push(op('Expr', values[i]));
           } else {
             throw new Error(`SYNTAX ERROR: #in-element does not take a \`${keys[0]}\` option`);
diff --git a/packages/@glimmer/runtime/lib/compiled/opcodes/dom.ts b/packages/@glimmer/runtime/lib/compiled/opcodes/dom.ts
index 944cdd40b..006a37ee8 100644
--- a/packages/@glimmer/runtime/lib/compiled/opcodes/dom.ts
+++ b/packages/@glimmer/runtime/lib/compiled/opcodes/dom.ts
@@ -7,9 +7,8 @@ import {
   isConst,
   isConstTag,
 } from '@glimmer/reference';
-import { Option } from '@glimmer/util';
-import { check, CheckString, CheckElement, CheckNode, CheckOption } from '@glimmer/debug';
-import { Op } from '@glimmer/interfaces';
+import { check, CheckString, CheckElement } from '@glimmer/debug';
+import { Op, Option } from '@glimmer/interfaces';
 import { $t0 } from '@glimmer/vm';
 import {
   ModifierDefinition,
@@ -22,7 +21,7 @@ import { Assert } from './vm';
 import { DynamicAttribute } from '../../vm/attributes/dynamic';
 import { CheckReference, CheckArguments, CheckOperations } from './-debug-strip';
 import { CONSTANTS } from '../../symbols';
-import { SimpleElement, SimpleNode } from '@simple-dom/interface';
+import { SimpleElement } from '@simple-dom/interface';
 
 APPEND_OPCODES.add(Op.Text, (vm, { op1: text }) => {
   vm.elements().appendText(vm[CONSTANTS].getString(text));
@@ -43,11 +42,10 @@ APPEND_OPCODES.add(Op.OpenDynamicElement, vm => {
 
 APPEND_OPCODES.add(Op.PushRemoteElement, vm => {
   let elementRef = check(vm.stack.pop(), CheckReference);
-  let nextSiblingRef = check(vm.stack.pop(), CheckReference);
+  let insertBeforeRef = check(vm.stack.pop(), CheckReference);
   let guidRef = check(vm.stack.pop(), CheckReference);
 
   let element: SimpleElement;
-  let nextSibling: Option<SimpleNode>;
   let guid = guidRef.value() as string;
 
   if (isConst(elementRef)) {
@@ -58,15 +56,9 @@ APPEND_OPCODES.add(Op.PushRemoteElement, vm => {
     vm.updateWith(new Assert(cache));
   }
 
-  if (isConst(nextSiblingRef)) {
-    nextSibling = check(nextSiblingRef.value(), CheckOption(CheckNode));
-  } else {
-    let cache = new ReferenceCache(nextSiblingRef as Reference<Option<SimpleNode>>);
-    nextSibling = check(cache.peek(), CheckOption(CheckNode));
-    vm.updateWith(new Assert(cache));
-  }
+  let insertBefore = insertBeforeRef.value() as Option<null>;
 
-  let block = vm.elements().pushRemoteElement(element, guid, nextSibling);
+  let block = vm.elements().pushRemoteElement(element, guid, insertBefore);
   if (block) vm.associateDestroyable(block);
 });
 
diff --git a/packages/@glimmer/runtime/lib/vm/element-builder.ts b/packages/@glimmer/runtime/lib/vm/element-builder.ts
index 66bd2fb37..8941fb4b1 100644
--- a/packages/@glimmer/runtime/lib/vm/element-builder.ts
+++ b/packages/@glimmer/runtime/lib/vm/element-builder.ts
@@ -205,18 +205,26 @@ export class NewElementBuilder implements ElementBuilder {
   pushRemoteElement(
     element: SimpleElement,
     guid: string,
-    nextSibling: Option<SimpleNode> = null
+    insertBefore: Option<null>
   ): Option<RemoteLiveBlock> {
-    return this.__pushRemoteElement(element, guid, nextSibling);
+    return this.__pushRemoteElement(element, guid, insertBefore);
   }
 
   __pushRemoteElement(
     element: SimpleElement,
     _guid: string,
-    nextSibling: Option<SimpleNode>
+    insertBefore: Option<null>
   ): Option<RemoteLiveBlock> {
-    this.pushElement(element, nextSibling);
+    this.pushElement(element, insertBefore);
+
+    if (insertBefore === undefined) {
+      while (element.lastChild) {
+        element.removeChild(element.lastChild);
+      }
+    }
+
     let block = new RemoteLiveBlock(element);
+
     return this.pushLiveBlock(block, true);
   }
 
diff --git a/packages/@glimmer/runtime/lib/vm/rehydrate-builder.ts b/packages/@glimmer/runtime/lib/vm/rehydrate-builder.ts
index d6634e832..c5ba914f3 100644
--- a/packages/@glimmer/runtime/lib/vm/rehydrate-builder.ts
+++ b/packages/@glimmer/runtime/lib/vm/rehydrate-builder.ts
@@ -379,15 +379,21 @@ export class RehydrateBuilder extends NewElementBuilder implements ElementBuilde
   __pushRemoteElement(
     element: SimpleElement,
     cursorId: string,
-    nextSibling: Option<SimpleNode> = null
+    insertBefore: Option<null>
   ): Option<RemoteLiveBlock> {
     let marker = this.getMarker(element as HTMLElement, cursorId);
 
     if (marker.parentNode === element) {
+      if (insertBefore === undefined) {
+        while (element.lastChild !== marker) {
+          element.removeChild(element.lastChild!);
+        }
+      }
+
       let currentCursor = this.currentCursor;
       let candidate = currentCursor!.candidate;
 
-      this.pushElement(element, nextSibling);
+      this.pushElement(element, insertBefore);
 
       currentCursor!.candidate = candidate;
       this.candidate = this.remove(marker);
diff --git a/packages/@glimmer/syntax/lib/parser/handlebars-node-visitors.ts b/packages/@glimmer/syntax/lib/parser/handlebars-node-visitors.ts
index 029b7ae9e..e86b50369 100644
--- a/packages/@glimmer/syntax/lib/parser/handlebars-node-visitors.ts
+++ b/packages/@glimmer/syntax/lib/parser/handlebars-node-visitors.ts
@@ -441,14 +441,18 @@ function addElementModifier(element: Tag<'StartTag'>, mustache: AST.MustacheStat
 }
 
 function addInElementHash(cursor: string, hash: AST.Hash, loc: AST.SourceLocation) {
-  let hasNextSibling = false;
+  let hasInsertBefore = false;
   hash.pairs.forEach(pair => {
     if (pair.key === 'guid') {
       throw new SyntaxError('Cannot pass `guid` from user space', loc);
     }
 
-    if (pair.key === 'nextSibling') {
-      hasNextSibling = true;
+    if (pair.key === 'insertBefore') {
+      if (pair.value.type !== 'NullLiteral') {
+        throw new SyntaxError('insertBefore only takes `null` as an argument', loc);
+      }
+
+      hasInsertBefore = true;
     }
   });
 
@@ -456,10 +460,10 @@ function addInElementHash(cursor: string, hash: AST.Hash, loc: AST.SourceLocatio
   let guidPair = b.pair('guid', guid);
   hash.pairs.unshift(guidPair);
 
-  if (!hasNextSibling) {
-    let nullLiteral = b.literal('NullLiteral', null);
-    let nextSibling = b.pair('nextSibling', nullLiteral);
-    hash.pairs.push(nextSibling);
+  if (!hasInsertBefore) {
+    let undefinedLiteral = b.literal('UndefinedLiteral', undefined);
+    let beforeSibling = b.pair('insertBefore', undefinedLiteral);
+    hash.pairs.push(beforeSibling);
   }
 
   return hash;