diff --git a/package.json b/package.json
index 1880710..23d5dff 100644
--- a/package.json
+++ b/package.json
@@ -26,7 +26,7 @@
         "lodash":      "4.x",
         "node-getopt": "0.2.x",
         "source-map":  "0.5.x",
-        "typescript":  "3.9.x"
+        "typescript":  "4.9"
     },
     "scripts": {
         "test": "mocha --ui tdd"
diff --git a/src/typechecker/DiagnosticParser.js b/src/typechecker/DiagnosticParser.js
index c7699b2..39d0a60 100644
--- a/src/typechecker/DiagnosticParser.js
+++ b/src/typechecker/DiagnosticParser.js
@@ -222,20 +222,22 @@ getWarnings(diagnostics, fileCallback)
         fileName = fileCallback(fileName);
         if (!fileName) return null;
 
-        let result = {
-            code:   code,
-            column: lineColumn.column,
-            name:   NSWarning.Typechecker,
-            file:   fileName,
-            line:   lineNumber,
-            reason: reason 
-        };
-
         // Only return if this error message is unique (defs can spam duplicate messages)
-        let key = result.file + ":" + result.line + ":" + result.reason;
+        let key = fileName + ":" + lineNumber + ":" + reason;
+
         if (!duplicateMap[key]) {
             duplicateMap[key] = true;
-            return result;
+
+            let error = new Error(reason);
+
+            error.name   = NSWarning.Typechecker;
+            error.file   = fileName;
+            error.line   = lineNumber;
+            error.column = lineColumn.column;
+            error.reason = reason;
+            error.code   = code;
+
+            return error;
         }
 
         return null;
diff --git a/src/typechecker/Typechecker.js b/src/typechecker/Typechecker.js
index cebfc85..0f3d795 100644
--- a/src/typechecker/Typechecker.js
+++ b/src/typechecker/Typechecker.js
@@ -165,6 +165,8 @@ async check(model, defs, files)
             return sourceFile;
         },
 
+        fileExists:                () => { return false; },
+        readFile:                  () => { },
         writeFile:                 () => { },
         getDefaultLibFileName:     options => ts.getDefaultLibFilePath(options),
         useCaseSensitiveFileNames: () => false,