diff --git a/src/utils/ast.js b/src/utils/ast.js
index 5157dedc74..f2cab903eb 100644
--- a/src/utils/ast.js
+++ b/src/utils/ast.js
@@ -8,21 +8,20 @@ import { xor, range } from "lodash";
 import { convertToList } from "./pause/pausePoints";
 
 import type { Location, Source, ColumnPosition } from "../types";
+import type { Symbols } from "../reducers/ast";
 
-import type {
-  AstPosition,
-  AstLocation,
-  PausePoints,
-  SymbolDeclarations
-} from "../workers/parser";
+import type { AstPosition, AstLocation, PausePoints } from "../workers/parser";
 
 export function findBestMatchExpression(
-  symbols: SymbolDeclarations,
+  symbols: Symbols,
   tokenPos: ColumnPosition
 ) {
-  const { memberExpressions, identifiers, literals } = symbols;
-  const { line, column } = tokenPos;
+  if (symbols.loading) {
+    return null;
+  }
 
+  const { line, column } = tokenPos;
+  const { memberExpressions, identifiers, literals } = symbols;
   const members = memberExpressions.filter(({ computed }) => !computed);
 
   return []
@@ -107,18 +106,18 @@ function findClosestofSymbol(declarations: any[], location: Location) {
   }, null);
 }
 
-export function findClosestFunction(
-  symbols: SymbolDeclarations,
-  location: Location
-) {
-  const { functions } = symbols;
-  return findClosestofSymbol(functions, location);
+export function findClosestFunction(symbols: ?Symbols, location: Location) {
+  if (!symbols || symbols.loading) {
+    return null;
+  }
+
+  return findClosestofSymbol(symbols.functions, location);
 }
 
-export function findClosestClass(
-  symbols: SymbolDeclarations,
-  location: Location
-) {
-  const { classes } = symbols;
-  return findClosestofSymbol(classes, location);
+export function findClosestClass(symbols: Symbols, location: Location) {
+  if (!symbols || symbols.loading) {
+    return null;
+  }
+
+  return findClosestofSymbol(symbols.functions, location);
 }
diff --git a/src/utils/function.js b/src/utils/function.js
index 96f37abef2..d224a2ca5c 100644
--- a/src/utils/function.js
+++ b/src/utils/function.js
@@ -2,21 +2,28 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
 
+// @flow
 import { findClosestFunction } from "./ast";
 import { correctIndentation } from "./indentation";
+import type { Source } from "../types";
+import type { Symbols } from "../reducers/ast";
 
-export function findFunctionText(line, source, symbols) {
+export function findFunctionText(
+  line: number,
+  source: Source,
+  symbols: ?Symbols
+): ?string {
   const func = findClosestFunction(symbols, {
+    sourceId: source.id,
     line,
     column: Infinity
   });
-  if (!func) {
+
+  if (!func || !source.text) {
     return null;
   }
 
-  const {
-    location: { start, end }
-  } = func;
+  const { location: { start, end } } = func;
   const lines = source.text.split("\n");
   const firstLine = lines[start.line - 1].slice(start.column);
   const lastLine = lines[end.line - 1].slice(0, end.column);