diff --git a/src/generators/Generator.js b/src/generators/Generator.js
index bdf8de7278..d6056930e2 100644
--- a/src/generators/Generator.js
+++ b/src/generators/Generator.js
@@ -242,7 +242,7 @@ export default class Generator {
 
 	getUniqueName ( name ) {
 		let alias = name;
-		for ( let i = 1; reservedNames.has( alias ) || this.importedNames.has( alias ) || this._usedNames.has( alias ); alias = `${name}$${i++}` );
+		for ( let i = 1; reservedNames.has( alias ) || this.importedNames.has( alias ) || this._usedNames.has( alias ); alias = `${name}_${i++}` );
 		this._usedNames.add( alias );
 		return alias;
 	}
@@ -251,7 +251,7 @@ export default class Generator {
 		const localUsedNames = new Set( params );
 		return name => {
 			let alias = name;
-			for ( let i = 1; reservedNames.has( alias ) || this.importedNames.has( alias ) || this._usedNames.has( alias ) || localUsedNames.has( alias ); alias = `${name}$${i++}` );
+			for ( let i = 1; reservedNames.has( alias ) || this.importedNames.has( alias ) || this._usedNames.has( alias ) || localUsedNames.has( alias ); alias = `${name}_${i++}` );
 			localUsedNames.add( alias );
 			return alias;
 		};
@@ -296,7 +296,7 @@ export default class Generator {
 				} else {
 					const { declarations } = annotateWithScopes( js );
 					let template = 'template';
-					for ( let i = 1; declarations.has( template ); template = `template$${i++}` );
+					for ( let i = 1; declarations.has( template ); template = `template_${i++}` );
 
 					this.code.overwrite( defaultExport.start, defaultExport.declaration.start, `var ${template} = ` );
 
diff --git a/src/generators/dom/index.js b/src/generators/dom/index.js
index 233616e40f..32b9ec793d 100644
--- a/src/generators/dom/index.js
+++ b/src/generators/dom/index.js
@@ -78,7 +78,7 @@ class DomGenerator extends Generator {
 		} else {
 			properties.addBlock( deindent`
 				update: function ( changed, ${fragment.params.join( ', ' )} ) {
-					var __tmp;
+					${fragment.tmp ? `var ${fragment.tmp};` : ''}
 
 					${fragment.builders.update}
 				},
@@ -119,8 +119,9 @@ class DomGenerator extends Generator {
 		}
 	}
 
-	generateBlock ( node, name ) {
+	generateBlock ( node, name, type ) {
 		this.push({
+			type,
 			name,
 			target: 'target',
 			localElementDepth: 0,
@@ -203,7 +204,8 @@ export default function dom ( parsed, source, options ) {
 	const component = getUniqueName( 'component' );
 
 	generator.push({
-		name: generator.alias( 'renderMainFragment' ),
+		type: 'block',
+		name: generator.alias( 'render_main_fragment' ),
 		namespace,
 		target: 'target',
 		localElementDepth: 0,
@@ -241,7 +243,7 @@ export default function dom ( parsed, source, options ) {
 	}
 
 	builders._set.addLine( 'var oldState = this._state;' );
-	builders._set.addLine( 'this._state = Object.assign( {}, oldState, newState );' );
+	builders._set.addLine( `this._state = ${generator.helper( 'assign' )}( {}, oldState, newState );` );
 
 	if ( computations.length ) {
 		const builder = new CodeBuilder();
@@ -277,13 +279,13 @@ export default function dom ( parsed, source, options ) {
 
 	if ( generator.css && options.css !== false ) {
 		builders.main.addBlock( deindent`
-			var ${generator.alias( 'addedCss' )} = false;
-			function ${generator.alias( 'addCss' )} () {
+			var ${generator.alias( 'added_css' )} = false;
+			function ${generator.alias( 'add_css' )} () {
 				var style = ${generator.helper( 'createElement' )}( 'style' );
 				style.textContent = ${JSON.stringify( generator.css )};
 				${generator.helper( 'appendNode' )}( style, document.head );
 
-				${generator.alias( 'addedCss' )} = true;
+				${generator.alias( 'added_css' )} = true;
 			}
 		` );
 	}
@@ -294,7 +296,7 @@ export default function dom ( parsed, source, options ) {
 	builders.init.addLine( `this._torndown = false;` );
 
 	if ( parsed.css && options.css !== false ) {
-		builders.init.addLine( `if ( !${generator.alias( 'addedCss' )} ) ${generator.alias( 'addCss' )}();` );
+		builders.init.addLine( `if ( !${generator.alias( 'added_css' )} ) ${generator.alias( 'add_css' )}();` );
 	}
 
 	if ( generator.hasComponents ) {
@@ -304,7 +306,7 @@ export default function dom ( parsed, source, options ) {
 	if ( generator.hasComplexBindings ) {
 		builders.init.addBlock( deindent`
 			this._bindings = [];
-			this._fragment = ${generator.alias( 'renderMainFragment' )}( this._state, this );
+			this._fragment = ${generator.alias( 'render_main_fragment' )}( this._state, this );
 			if ( options.target ) this._fragment.mount( options.target, null );
 			while ( this._bindings.length ) this._bindings.pop()();
 		` );
@@ -312,7 +314,7 @@ export default function dom ( parsed, source, options ) {
 		builders._set.addLine( `while ( this._bindings.length ) this._bindings.pop()();` );
 	} else {
 		builders.init.addBlock( deindent`
-			this._fragment = ${generator.alias( 'renderMainFragment' )}( this._state, this );
+			this._fragment = ${generator.alias( 'render_main_fragment' )}( this._state, this );
 			if ( options.target ) this._fragment.mount( options.target, null );
 		` );
 	}
@@ -340,7 +342,7 @@ export default function dom ( parsed, source, options ) {
 	if ( generator.usesRefs ) constructorBlock.addLine( `this.refs = {};` );
 
 	constructorBlock.addLine(
-		`this._state = ${templateProperties.data ? `Object.assign( ${generator.alias( 'template' )}.data(), options.data )` : `options.data || {}`};`
+		`this._state = ${templateProperties.data ? `${generator.helper( 'assign' )}( ${generator.alias( 'template' )}.data(), options.data )` : `options.data || {}`};`
 	);
 
 	if ( !generator.builders.metaBindings.isEmpty() ) {
@@ -393,7 +395,7 @@ export default function dom ( parsed, source, options ) {
 
 	if ( sharedPath ) {
 		const base = templateProperties.methods ? `{}, ${generator.alias( 'template' )}.methods` : `{}`;
-		builders.main.addBlock( `${name}.prototype = Object.assign( ${base}, ${generator.helper( 'proto' )} );` );
+		builders.main.addBlock( `${name}.prototype = ${generator.helper( 'assign' )}( ${base}, ${generator.helper( 'proto' )} );` );
 	} else {
 		if ( templateProperties.methods ) {
 			builders.main.addBlock( `${name}.prototype = ${generator.alias( 'template' )}.methods;` );
diff --git a/src/generators/dom/utils/findBlock.js b/src/generators/dom/utils/findBlock.js
new file mode 100644
index 0000000000..59f71e3552
--- /dev/null
+++ b/src/generators/dom/utils/findBlock.js
@@ -0,0 +1,4 @@
+export default function findBlock ( fragment ) {
+	while ( fragment.type !== 'block' ) fragment = fragment.parent;
+	return fragment;
+}
\ No newline at end of file
diff --git a/src/generators/dom/visitors/Component.js b/src/generators/dom/visitors/Component.js
index d7849e9438..69e2e3c2ac 100644
--- a/src/generators/dom/visitors/Component.js
+++ b/src/generators/dom/visitors/Component.js
@@ -76,12 +76,12 @@ export default {
 
 		// Component has children, put them in a separate {{yield}} block
 		if ( hasChildren ) {
-			const yieldName = generator.getUniqueName( `render${name}YieldFragment` );
+			const yieldName = generator.getUniqueName( `render_${name}_yield_fragment` );
 			const params = current.params.join( ', ' );
 
-			generator.generateBlock( node, yieldName );
+			generator.generateBlock( node, yieldName, 'block' );
 
-			const yieldFragment = current.getUniqueName( `${name}_yieldFragment` );
+			const yieldFragment = current.getUniqueName( `${name}_yield_fragment` );
 
 			current.builders.init.addLine(
 				`var ${yieldFragment} = ${yieldName}( ${params}, ${current.component} );`
@@ -104,9 +104,9 @@ export default {
 			const initialPropString = stringifyProps( initialProps );
 
 			if ( local.bindings.length ) {
-				const initialData = current.getUniqueName( `${name}_initialData` );
+				const initialData = current.getUniqueName( `${name}_initial_data` );
 
-				statements.push( `var ${name}_initialData = ${initialPropString};` );
+				statements.push( `var ${name}_initial_data = ${initialPropString};` );
 
 				local.bindings.forEach( binding => {
 					statements.push( `if ( ${binding.prop} in ${binding.obj} ) ${initialData}.${binding.name} = ${binding.value};` );
@@ -159,6 +159,7 @@ export default {
 		if ( !local.update.isEmpty() ) current.builders.update.addBlock( local.update );
 
 		generator.push({
+			type: 'component',
 			namespace: local.namespace,
 			target: name,
 			parent: current,
diff --git a/src/generators/dom/visitors/EachBlock.js b/src/generators/dom/visitors/EachBlock.js
index 2dc6f222c8..df9936197f 100644
--- a/src/generators/dom/visitors/EachBlock.js
+++ b/src/generators/dom/visitors/EachBlock.js
@@ -4,8 +4,8 @@ import getBuilders from '../utils/getBuilders.js';
 
 export default {
 	enter ( generator, node ) {
-		const name = generator.getUniqueName( `eachBlock` );
-		const renderer = generator.getUniqueName( `renderEachBlock` );
+		const name = generator.getUniqueName( `each_block` );
+		const renderer = generator.getUniqueName( `render_each_block` );
 		const elseName = generator.getUniqueName( `${name}_else` );
 		const renderElse = generator.getUniqueName( `${renderer}_else` );
 		const i = generator.current.getUniqueName( `i` );
@@ -168,11 +168,11 @@ export default {
 		}
 
 		if ( node.else ) {
-			generator.generateBlock( node.else, renderElse );
+			generator.generateBlock( node.else, renderElse, 'block' );
 		}
 
 		const indexNames = new Map( generator.current.indexNames );
-		const indexName = node.index || generator.current.getUniqueName( `${node.context}__index` );
+		const indexName = node.index || generator.current.getUniqueName( `${node.context}_index` );
 		indexNames.set( node.context, indexName );
 
 		const listNames = new Map( generator.current.listNames );
@@ -193,6 +193,7 @@ export default {
 		const getUniqueName = generator.getUniqueNameMaker( blockParams );
 
 		generator.push({
+			type: 'block',
 			name: renderer,
 			target: 'target',
 			expression: node.expression,
diff --git a/src/generators/dom/visitors/Element.js b/src/generators/dom/visitors/Element.js
index 478bc39e2e..566a535bab 100644
--- a/src/generators/dom/visitors/Element.js
+++ b/src/generators/dom/visitors/Element.js
@@ -101,6 +101,7 @@ export default {
 		generator.createMountStatement( name );
 
 		generator.push({
+			type: 'element',
 			namespace: local.namespace,
 			target: name,
 			parent: generator.current,
diff --git a/src/generators/dom/visitors/IfBlock.js b/src/generators/dom/visitors/IfBlock.js
index 81552588e5..0de7e936b2 100644
--- a/src/generators/dom/visitors/IfBlock.js
+++ b/src/generators/dom/visitors/IfBlock.js
@@ -9,7 +9,7 @@ function getConditionsAndBlocks ( generator, node, _name, i = 0 ) {
 		block: name
 	}];
 
-	generator.generateBlock( node, name );
+	generator.generateBlock( node, name, 'block' );
 
 	if ( node.else && node.else.children.length === 1 &&
 		node.else.children[0].type === 'IfBlock' ) {
@@ -24,7 +24,7 @@ function getConditionsAndBlocks ( generator, node, _name, i = 0 ) {
 		});
 
 		if ( node.else ) {
-			generator.generateBlock( node.else, name );
+			generator.generateBlock( node.else, name, 'block' );
 		}
 	}
 	return conditionsAndBlocks;
@@ -33,13 +33,13 @@ function getConditionsAndBlocks ( generator, node, _name, i = 0 ) {
 export default {
 	enter ( generator, node ) {
 		const params = generator.current.params.join( ', ' );
-		const name = generator.getUniqueName( `ifBlock` );
-		const getBlock = generator.current.getUniqueName( `getBlock` );
-		const currentBlock = generator.current.getUniqueName( `currentBlock` );
-		const _currentBlock = generator.current.getUniqueName( `_currentBlock` );
+		const name = generator.getUniqueName( `if_block` );
+		const getBlock = generator.current.getUniqueName( `get_block` );
+		const currentBlock = generator.current.getUniqueName( `current_block` );
+		const _currentBlock = generator.current.getUniqueName( `_current_block` );
 
 		const isToplevel = generator.current.localElementDepth === 0;
-		const conditionsAndBlocks = getConditionsAndBlocks( generator, node, generator.getUniqueName( `renderIfBlock` ) );
+		const conditionsAndBlocks = getConditionsAndBlocks( generator, node, generator.getUniqueName( `render_if_block` ) );
 
 		const anchor = `${name}_anchor`;
 		generator.createAnchor( anchor );
diff --git a/src/generators/dom/visitors/MustacheTag.js b/src/generators/dom/visitors/MustacheTag.js
index 35ec8ddee3..6e0ba72e63 100644
--- a/src/generators/dom/visitors/MustacheTag.js
+++ b/src/generators/dom/visitors/MustacheTag.js
@@ -1,4 +1,5 @@
 import deindent from '../../../utils/deindent.js';
+import findBlock from '../utils/findBlock.js';
 
 export default {
 	enter ( generator, node ) {
@@ -9,9 +10,12 @@ export default {
 		generator.current.builders.init.addLine( `var last_${name} = ${snippet};` );
 		generator.addElement( name, `${generator.helper( 'createText' )}( last_${name} )`, true );
 
+		const fragment = findBlock( generator.current );
+		if ( !fragment.tmp ) fragment.tmp = fragment.getUniqueName( 'tmp' );
+
 		generator.current.builders.update.addBlock( deindent`
-			if ( ( __tmp = ${snippet} ) !== last_${name} ) {
-				${name}.data = last_${name} = __tmp;
+			if ( ( ${fragment.tmp} = ${snippet} ) !== last_${name} ) {
+				${name}.data = last_${name} = ${fragment.tmp};
 			}
 		` );
 	}
diff --git a/src/generators/dom/visitors/RawMustacheTag.js b/src/generators/dom/visitors/RawMustacheTag.js
index 5f2d54c0e0..2a5cf46381 100644
--- a/src/generators/dom/visitors/RawMustacheTag.js
+++ b/src/generators/dom/visitors/RawMustacheTag.js
@@ -1,4 +1,5 @@
 import deindent from '../../../utils/deindent.js';
+import findBlock from '../utils/findBlock.js';
 
 export default {
 	enter ( generator, node ) {
@@ -26,9 +27,12 @@ export default {
 			generator.current.builders.init.addLine( mountStatement );
 		}
 
+		const fragment = findBlock( generator.current );
+		if ( !fragment.tmp ) fragment.tmp = fragment.getUniqueName( 'tmp' );
+
 		generator.current.builders.update.addBlock( deindent`
-			if ( ( __tmp = ${snippet} ) !== last_${name} ) {
-				last_${name} = __tmp;
+			if ( ( ${fragment.tmp} = ${snippet} ) !== last_${name} ) {
+				last_${name} = ${fragment.tmp};
 				${detachStatement}
 				${mountStatement}
 			}
diff --git a/src/generators/dom/visitors/attributes/addElementAttributes.js b/src/generators/dom/visitors/attributes/addElementAttributes.js
index 1f1132aa73..2d96cc73bf 100644
--- a/src/generators/dom/visitors/attributes/addElementAttributes.js
+++ b/src/generators/dom/visitors/attributes/addElementAttributes.js
@@ -3,6 +3,7 @@ import addElementBinding from './addElementBinding';
 import deindent from '../../../../utils/deindent.js';
 import flattenReference from '../../../../utils/flattenReference.js';
 import getStaticAttributeValue from './binding/getStaticAttributeValue.js';
+import findBlock from '../../utils/findBlock.js';
 
 export default function addElementAttributes ( generator, node, local ) {
 	node.attributes.forEach( attribute => {
@@ -105,9 +106,12 @@ export default function addElementAttributes ( generator, node, local ) {
 					}
 
 					local.init.addLine( updater );
+					const fragment = findBlock( generator.current );
+					if ( !fragment.tmp ) fragment.tmp = fragment.getUniqueName( 'tmp' );
+
 					local.update.addBlock( deindent`
-						if ( ( __tmp = ${snippet} ) !== ${last} ) {
-							${last} = __tmp;
+						if ( ( ${fragment.tmp} = ${snippet} ) !== ${last} ) {
+							${last} = ${fragment.tmp};
 							${updater}
 						}
 					` );
@@ -177,7 +181,7 @@ export default function addElementAttributes ( generator, node, local ) {
 				return `var ${listName} = this.__svelte.${listName}, ${indexName} = this.__svelte.${indexName}, ${name} = ${listName}[${indexName}]`;
 			});
 
-			const handlerName = generator.current.getUniqueName( `${name}Handler` );
+			const handlerName = generator.current.getUniqueName( `${name}_handler` );
 			const handlerBody = ( declarations.length ? declarations.join( '\n' ) + '\n\n' : '' ) + `[✂${attribute.expression.start}-${attribute.expression.end}✂];`;
 
 			if ( generator.events.has( name ) ) {
diff --git a/src/generators/dom/visitors/attributes/addElementBinding.js b/src/generators/dom/visitors/attributes/addElementBinding.js
index e8a049570e..eea65eda93 100644
--- a/src/generators/dom/visitors/attributes/addElementBinding.js
+++ b/src/generators/dom/visitors/attributes/addElementBinding.js
@@ -13,7 +13,7 @@ export default function createBinding ( generator, node, attribute, current, loc
 		if ( !~local.allUsedContexts.indexOf( context ) ) local.allUsedContexts.push( context );
 	});
 
-	const handler = current.getUniqueName( `${local.name}ChangeHandler` );
+	const handler = current.getUniqueName( `${local.name}_change_handler` );
 
 	const isMultipleSelect = node.name === 'select' && node.attributes.find( attr => attr.name.toLowerCase() === 'multiple' ); // TODO use getStaticAttributeValue
 	const type = getStaticAttributeValue( node, 'type' );
diff --git a/src/shared/index.js b/src/shared/index.js
index 529435821b..1ce6b42ceb 100644
--- a/src/shared/index.js
+++ b/src/shared/index.js
@@ -3,6 +3,15 @@ export * from './methods.js';
 
 export function noop () {}
 
+export function assign ( target ) {
+	for ( var i = 1; i < arguments.length; i += 1 ) {
+		var source = arguments[i];
+		for ( var k in source ) target[k] = source[k];
+	}
+
+	return target;
+}
+
 export function differs ( a, b ) {
 	return ( a !== b ) || ( a && ( typeof a === 'object' ) || ( typeof a === 'function' ) );
 }
diff --git a/test/generator/index.js b/test/generator/index.js
index 04599c6f2b..8ee4280828 100644
--- a/test/generator/index.js
+++ b/test/generator/index.js
@@ -30,6 +30,8 @@ require.extensions[ '.html' ] = function ( module, filename ) {
 	return module._compile( code, filename );
 };
 
+const Object_assign = Object.assign;
+
 describe( 'generate', () => {
 	before( setupHtmlEqual );
 
@@ -67,7 +69,7 @@ describe( 'generate', () => {
 			// check that no ES2015+ syntax slipped in
 			if ( !config.allowES2015 ) {
 				try {
-					const startIndex = code.indexOf( 'function renderMainFragment' ); // may change!
+					const startIndex = code.indexOf( 'function render_main_fragment' ); // may change!
 					const es5 = spaces( startIndex ) + code.slice( startIndex ).replace( /export default .+/, '' );
 					acorn.parse( es5, { ecmaVersion: 5 });
 				} catch ( err ) {
@@ -93,6 +95,10 @@ describe( 'generate', () => {
 
 			return env()
 				.then( window => {
+					Object.assign = () => {
+						throw new Error( 'cannot use Object.assign in generated code, as it is not supported everywhere' );
+					};
+
 					global.window = window;
 
 					// Put the constructor on window for testing
@@ -145,6 +151,9 @@ describe( 'generate', () => {
 						if ( !config.show ) console.log( addLineNumbers( code ) ); // eslint-disable-line no-console
 						throw err;
 					}
+				})
+				.then( () => {
+					Object.assign = Object_assign;
 				});
 		});
 	}