diff --git a/src/generators/dom/Block.js b/src/generators/dom/Block.js
index f2d507c035..c8327e0b5d 100644
--- a/src/generators/dom/Block.js
+++ b/src/generators/dom/Block.js
@@ -176,7 +176,7 @@ export default class Block {
 		}
 
 		if ( this.hasIntroTransitions ) {
-			if ( this.builders.outro.isEmpty() ) {
+			if ( this.builders.intro.isEmpty() ) {
 				properties.addBlock( `intro: ${this.generator.helper( 'noop' )},` );
 			} else {
 				properties.addBlock( deindent`
diff --git a/src/generators/dom/index.js b/src/generators/dom/index.js
index fcd36fcba2..ea2bc706b8 100644
--- a/src/generators/dom/index.js
+++ b/src/generators/dom/index.js
@@ -303,22 +303,19 @@ export default function dom ( parsed, source, options ) {
 				}
 			});
 
-			if ( typeof value === 'function' ) { // exclude transitionManager — special case
+			if ( key === 'transitionManager' ) { // special case
+				const global = `_svelteTransitionManager`;
+
+				builders.main.addBlock(
+					`var ${generator.alias( 'transitionManager' )} = window.${global} || ( window.${global} = ${code});`
+				);
+			} else {
 				const alias = generator.alias( fn.id.name );
 				if ( alias !== fn.id.name ) code.overwrite( fn.id.start, fn.id.end, alias );
 
 				builders.main.addBlock( code.toString() );
 			}
 		});
-
-		if ( generator.hasIntroTransitions || generator.hasOutroTransitions ) {
-			const global = `_svelteTransitionManager`;
-			const transitionManager = toSource( shared.transitionManager );
-
-			builders.main.addBlock(
-				`var ${generator.alias( 'transitionManager' )} = window.${global} || ( window.${global} = ${transitionManager});`
-			);
-		}
 	}
 
 	return generator.generate( builders.main.toString(), options, { name, format } );
diff --git a/src/shared/transitions.js b/src/shared/transitions.js
index ddf3c55b3b..01a13b77ec 100644
--- a/src/shared/transitions.js
+++ b/src/shared/transitions.js
@@ -44,7 +44,7 @@ export function wrapTransition ( node, fn, params, intro, outgroup ) {
 
 		return assign( transition, {
 			update: function ( now ) {
-				const p = now - this.start;
+				var p = now - this.start;
 				this.t = this.a + this.d * ease( p / this.duration );
 				obj.tick( this.t );
 			},
@@ -94,7 +94,7 @@ export function wrapTransition ( node, fn, params, intro, outgroup ) {
 				.join( ', ' );
 		},
 		update: function ( now ) {
-			const p = now - this.start;
+			var p = now - this.start;
 			this.t = this.a + this.d * ease( p / this.duration );
 		},
 		done: function () {
diff --git a/test/runtime/index.js b/test/runtime/index.js
index e67192cbc6..153d8100f3 100644
--- a/test/runtime/index.js
+++ b/test/runtime/index.js
@@ -90,17 +90,19 @@ describe( 'runtime', () => {
 
 			let SvelteComponent;
 
-			try {
-				SvelteComponent = require( `./samples/${dir}/main.html` ).default;
-			} catch ( err ) {
-				if ( !config.show ) console.log( addLineNumbers( code ) ); // eslint-disable-line no-console
-				throw err;
-			}
-
 			let unintendedError = null;
 
 			return env()
 				.then( window => {
+					global.window = window;
+
+					try {
+						SvelteComponent = require( `./samples/${dir}/main.html` ).default;
+					} catch ( err ) {
+						if ( !config.show ) console.log( addLineNumbers( code ) ); // eslint-disable-line no-console
+						throw err;
+					}
+
 					Object.assign = () => {
 						throw new Error( 'cannot use Object.assign in generated code, as it is not supported everywhere' );
 					};
diff --git a/test/runtime/samples/transition-intro/_config.js b/test/runtime/samples/transition-intro-js/_config.js
similarity index 89%
rename from test/runtime/samples/transition-intro/_config.js
rename to test/runtime/samples/transition-intro-js/_config.js
index bb60ad0e80..18bd552663 100644
--- a/test/runtime/samples/transition-intro/_config.js
+++ b/test/runtime/samples/transition-intro-js/_config.js
@@ -4,7 +4,7 @@ export default {
 		let callback;
 
 		window.performance = { now: () => now };
-		window.requestAnimationFrame = cb => callback = cb;
+		global.requestAnimationFrame = cb => callback = cb;
 
 		component.set({ visible: true });
 		const div = target.querySelector( 'div' );
diff --git a/test/runtime/samples/transition-intro-js/main.html b/test/runtime/samples/transition-intro-js/main.html
new file mode 100644
index 0000000000..9a3b4f34b8
--- /dev/null
+++ b/test/runtime/samples/transition-intro-js/main.html
@@ -0,0 +1,18 @@
+{{#if visible}}
+	<div in:fade>fades in</div>
+{{/if}}
+
+<script>
+	export default {
+		transitions: {
+			fade: function ( node, params ) {
+				return {
+					duration: 400,
+					tick: t => {
+						node.style.opacity = t;
+					}
+				};
+			}
+		}
+	};
+</script>
\ No newline at end of file
diff --git a/test/runtime/samples/transition-intro/main.html b/test/runtime/samples/transition-intro/main.html
deleted file mode 100644
index 80cd4aca49..0000000000
--- a/test/runtime/samples/transition-intro/main.html
+++ /dev/null
@@ -1,3 +0,0 @@
-{{#if visible}}
-	<div in:style='{opacity: 0}'>fades in</div>
-{{/if}}
\ No newline at end of file