diff --git a/flow-typed/debugger-html.js b/flow-typed/debugger-html.js
index 48edaea7dc..ce424270b6 100644
--- a/flow-typed/debugger-html.js
+++ b/flow-typed/debugger-html.js
@@ -216,19 +216,6 @@ declare module "debugger-html" {
     loading?: boolean
   };
 
-  /**
-   * SourceText
-   * @memberof types
-   * @static
-   */
-  declare type SourceText = {
-    id: string,
-    text: string,
-    contentType: string,
-    loading?: boolean,
-    error?: boolean
-  };
-
   /**
  * Script
  * This describes scripts which are sent to the debug server to be eval'd
diff --git a/src/actions/sources.js b/src/actions/sources.js
index 0076c4a3c0..fe80bceb5c 100644
--- a/src/actions/sources.js
+++ b/src/actions/sources.js
@@ -34,7 +34,7 @@ import {
   removeSourceFromTabList
 } from "../selectors";
 
-import type { Source, SourceText } from "../types";
+import type { Source } from "../types";
 import type { ThunkArgs } from "./types";
 import type { State } from "../reducers/types";
 
@@ -358,13 +358,11 @@ export function loadSourceText(source: Source) {
 
         const response = await client.sourceContents(source.id);
 
-        const sourceText: SourceText = {
+        return {
           id: source.id,
           text: response.source,
           contentType: response.contentType || "text/javascript"
         };
-
-        return sourceText;
       })()
     });
 
diff --git a/src/actions/types.js b/src/actions/types.js
index 3531a69e46..56775588a4 100644
--- a/src/actions/types.js
+++ b/src/actions/types.js
@@ -7,7 +7,6 @@ import type {
   LoadedObject,
   Location,
   GeneratedLocation,
-  SourceText,
   Frame,
   Scope,
   Why
@@ -107,7 +106,7 @@ type SourceAction =
       source: Source,
       status: AsyncStatus,
       error: string,
-      value: SourceText
+      value: Source
     }
   | {
       type: "BLACKBOX",
@@ -123,7 +122,7 @@ type SourceAction =
       error: string,
       value: {
         isPrettyPrinted: boolean,
-        sourceText: SourceText,
+        source: Source,
         frames: Frame[]
       }
     }
@@ -216,7 +215,7 @@ type NavigateAction = { type: "NAVIGATE", url: string };
 type ASTAction =
   | {
       type: "SET_SYMBOLS",
-      source: SourceText,
+      source: Source,
       symbols: SymbolDeclaration[]
     }
   | {
diff --git a/src/reducers/sources.js b/src/reducers/sources.js
index 4fb9f9a3a7..a60913f00b 100644
--- a/src/reducers/sources.js
+++ b/src/reducers/sources.js
@@ -154,7 +154,7 @@ function update(
 
 function getTextPropsFromAction(action: any) {
   const source = action.source;
-  const sourceText = action.value;
+  const { value } = action;
 
   if (action.status === "start") {
     return { id: source.id, loading: true };
@@ -162,9 +162,9 @@ function getTextPropsFromAction(action: any) {
     return { id: source.id, error: action.error, loading: false };
   }
   return {
-    text: sourceText.text,
+    text: value.text,
     id: source.id,
-    contentType: sourceText.contentType,
+    contentType: value.contentType,
     loading: false
   };
 }
diff --git a/src/types.js b/src/types.js
index a7add8fca2..d3c1be22ed 100644
--- a/src/types.js
+++ b/src/types.js
@@ -31,7 +31,6 @@ export type {
   LoadedObject,
   Location,
   Source,
-  SourceText,
   Pause,
   Why
 } from "debugger-html";
diff --git a/src/utils/parser/getOutOfScopeLocations.js b/src/utils/parser/getOutOfScopeLocations.js
index 91fd1b24c5..6b66dca01e 100644
--- a/src/utils/parser/getOutOfScopeLocations.js
+++ b/src/utils/parser/getOutOfScopeLocations.js
@@ -1,6 +1,6 @@
 // @flow
 
-import type { SourceText } from "debugger-html";
+import type { Source } from "debugger-html";
 import type { AstLocation, AstPosition } from "./types";
 
 import get from "lodash/fp/get";
@@ -74,7 +74,7 @@ function sortByStart(a: AstLocation, b: AstLocation) {
  * location.
  */
 function getOutOfScopeLocations(
-  source: SourceText,
+  source: Source,
   position: AstPosition
 ): AstLocation[] {
   return findFunctions(source)
diff --git a/src/utils/parser/getSymbols.js b/src/utils/parser/getSymbols.js
index e719229aff..f30cdb15ec 100644
--- a/src/utils/parser/getSymbols.js
+++ b/src/utils/parser/getSymbols.js
@@ -6,7 +6,7 @@ import * as t from "babel-types";
 
 import getFunctionName from "./utils/getFunctionName";
 
-import type { SourceText } from "debugger-html";
+import type { Source } from "debugger-html";
 import type { NodePath, Node, Location as BabelLocation } from "babel-traverse";
 const symbolDeclarations = new Map();
 
@@ -58,7 +58,7 @@ function getVariableNames(path: NodePath): SymbolDeclaration[] {
   }));
 }
 
-export default function getSymbols(source: SourceText): SymbolDeclarations {
+export default function getSymbols(source: Source): SymbolDeclarations {
   if (symbolDeclarations.has(source.id)) {
     const symbols = symbolDeclarations.get(source.id);
     if (symbols) {
@@ -288,7 +288,7 @@ function getSnippet(path, prevPath, expression = "") {
   }
 }
 
-export function formatSymbols(source: SourceText) {
+export function formatSymbols(source: Source) {
   const {
     objectProperties,
     memberExpressions,
diff --git a/src/utils/parser/utils/ast.js b/src/utils/parser/utils/ast.js
index 60f9001b6d..0e09707e7e 100644
--- a/src/utils/parser/utils/ast.js
+++ b/src/utils/parser/utils/ast.js
@@ -6,7 +6,7 @@ import traverse from "babel-traverse";
 import isEmpty from "lodash/isEmpty";
 import { isDevelopment } from "devtools-config";
 
-import type { SourceText } from "debugger-html";
+import type { Source } from "debugger-html";
 
 const ASTs = new Map();
 
@@ -20,7 +20,7 @@ function _parse(code, opts) {
   );
 }
 
-function parse(text: string, opts?: Object) {
+function parse(text: ?string, opts?: Object) {
   let ast;
   if (!text) {
     return;
@@ -39,32 +39,37 @@ function parse(text: string, opts?: Object) {
   return ast;
 }
 
-export function getAst(sourceText: SourceText) {
-  if (ASTs.has(sourceText.id)) {
-    return ASTs.get(sourceText.id);
+// Custom parser for parse-script-tags that adapts its input structure to
+// our parser's signature
+function htmlParser({ source, line }) {
+  return parse(source, {
+    startLine: line
+  });
+}
+
+export function getAst(source: Source) {
+  if (!source || !source.text) {
+    return {};
+  }
+
+  if (ASTs.has(source.id)) {
+    return ASTs.get(source.id);
   }
 
   let ast = {};
-  if (sourceText.contentType == "text/html") {
-    // Custom parser for parse-script-tags that adapts its input structure to
-    // our parser's signature
-    const parser = ({ source, line }) => {
-      return parse(source, {
-        startLine: line
-      });
-    };
-    ast = parseScriptTags(sourceText.text, parser) || {};
-  } else if (sourceText.contentType == "text/javascript") {
-    ast = parse(sourceText.text);
+  if (source.contentType == "text/html") {
+    ast = parseScriptTags(source.text, htmlParser) || {};
+  } else if (source.contentType == "text/javascript") {
+    ast = parse(source.text);
   }
 
-  ASTs.set(sourceText.id, ast);
+  ASTs.set(source.id, ast);
   return ast;
 }
 
 type Visitor = { enter: Function };
-export function traverseAst(sourceText: SourceText, visitor: Visitor) {
-  const ast = getAst(sourceText);
+export function traverseAst(source: Source, visitor: Visitor) {
+  const ast = getAst(source);
   if (isEmpty(ast)) {
     return null;
   }
diff --git a/src/utils/parser/utils/closest.js b/src/utils/parser/utils/closest.js
index 8c50e848de..f1fd39a03d 100644
--- a/src/utils/parser/utils/closest.js
+++ b/src/utils/parser/utils/closest.js
@@ -9,7 +9,7 @@ import {
   nodeContainsPosition
 } from "./helpers";
 
-import type { SourceText, Location } from "debugger-html";
+import type { Source, Location } from "debugger-html";
 import type { NodePath, Node } from "babel-traverse";
 
 function getNodeValue(node: Node) {
@@ -43,7 +43,7 @@ function getClosestMemberExpression(source, token, location: Location) {
 }
 
 export function getClosestExpression(
-  source: SourceText,
+  source: Source,
   token: string,
   location: Location
 ) {
@@ -61,7 +61,7 @@ export function getClosestExpression(
   return { expression: getNodeValue(node), location: node.loc };
 }
 
-export function getClosestScope(source: SourceText, location: Location) {
+export function getClosestScope(source: Source, location: Location) {
   let closestPath = null;
 
   traverseAst(source, {
@@ -83,7 +83,7 @@ export function getClosestScope(source: SourceText, location: Location) {
   return closestPath.scope;
 }
 
-export function getClosestPath(source: SourceText, location: Location) {
+export function getClosestPath(source: Source, location: Location) {
   let closestPath = null;
 
   traverseAst(source, {