diff --git a/package-lock.json b/package-lock.json
index a2732ba0..582acfc6 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -127,9 +127,9 @@
       }
     },
     "monaco-editor-core": {
-      "version": "0.11.1",
-      "resolved": "https://registry.npmjs.org/monaco-editor-core/-/monaco-editor-core-0.11.1.tgz",
-      "integrity": "sha512-zbi+FI4Bm1B48AvAVjir0XUJlH85ZyFHaBcXvZjfy+mui8VaE7Run2ai/l9cvb6oqzTKQwg/UpYDu0BWyB8K5w==",
+      "version": "0.12.0",
+      "resolved": "https://registry.npmjs.org/monaco-editor-core/-/monaco-editor-core-0.12.0.tgz",
+      "integrity": "sha512-wOoEVAoZtrarDRcQC32Fp0ocacpQd6/Nb0FmUZOHeD3swZuPZhDLOxTyoNLjKq3d+h/6g+IARBLnDaLT5OQD4g==",
       "dev": true
     },
     "monaco-plugin-helpers": {
diff --git a/package.json b/package.json
index abc6845c..6900edaa 100644
--- a/package.json
+++ b/package.json
@@ -22,7 +22,7 @@
   },
   "devDependencies": {
     "mocha": "^2.5.3",
-    "monaco-editor-core": "0.11.1",
+    "monaco-editor-core": "0.12.0",
     "monaco-plugin-helpers": "^1.0.2",
     "requirejs": "^2.3.5",
     "typescript": "2.7.2",
diff --git a/src/languageFeatures.ts b/src/languageFeatures.ts
index df0a7668..44de5b71 100644
--- a/src/languageFeatures.ts
+++ b/src/languageFeatures.ts
@@ -148,7 +148,7 @@ export class DiagnostcsAdapter extends Adapter {
 		const {lineNumber: endLineNumber, column: endColumn} = this._offsetToPosition(resource, diag.start + diag.length);
 
 		return {
-			severity: monaco.Severity.Error,
+			severity: monaco.MarkerSeverity.Error,
 			startLineNumber,
 			startColumn,
 			endLineNumber,