diff --git a/package.json b/package.json
index c831885..f842563 100644
--- a/package.json
+++ b/package.json
@@ -25,7 +25,7 @@
   },
   "homepage": "https://github.com/screepers/screeps-typescript-starter#readme",
   "devDependencies": {
-    "@types/lodash": "^4.14.85",
+    "@types/lodash": "^3.10.1",
     "@types/source-map": "^0.5.2",
     "rollup": "^0.51.8",
     "rollup-plugin-clean": "^1.0.0",
diff --git a/src/main.ts b/src/main.ts
index 877401a..25d3bbe 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -1,16 +1,14 @@
 import { ErrorMapper } from "utils/ErrorMapper";
 
-export function loop() {
-  try {
-    // Clear non-existing creep memory.
-    for (const name in Memory.creeps) {
-      if (!Game.creeps[name]) {
-        delete Memory[name];
-      }
-    }
+// When compiling TS to JS and bundling with rollup, the line numbers and file names in error messages change
+// This utility uses source maps to get the line numbers and file names of the original, TS source code
+export const loop = ErrorMapper.wrapLoop(function() {
+  console.log(`Current game tick is ${Game.time}`);
 
-    console.log(`Current tick is ${Game.time}`);
-  } catch (e) {
-    console.log(ErrorMapper.sourceMappedStackTrace(e));
+  // Automatically delete memory of missing creeps
+  for (let name in Memory.creeps) {
+    if (!(name in Game.creeps)) {
+      delete Memory.creeps[name];
+    }
   }
-}
+});
diff --git a/src/utils/ErrorMapper.ts b/src/utils/ErrorMapper.ts
index 91475ab..405f44c 100644
--- a/src/utils/ErrorMapper.ts
+++ b/src/utils/ErrorMapper.ts
@@ -67,4 +67,23 @@ export class ErrorMapper {
     this.cache[stack] = outStack;
     return outStack;
   }
+
+  public static wrapLoop(loop: () => void): () => void {
+    return () => {
+      try {
+        loop();
+      } catch (e) {
+        if (e instanceof Error) {
+          if ("sim" in Game.rooms) {
+            console.log(`<span style='color:red'>Source maps don't work in the simulator - displaying original error<br>${_.escape(e.stack)}</span>`)
+          } else {
+            console.log(`<span style='color:red'>${_.escape(this.sourceMappedStackTrace(e))}</span>`);
+          }
+        } else {
+          // can't handle it
+          throw e;
+        }
+      }
+    }
+  }
 }