diff --git a/package.json b/package.json
index 87fa61b..a41af7e 100644
--- a/package.json
+++ b/package.json
@@ -63,7 +63,7 @@
       "webpack-dev-server": "3.11.0",
       "extract-loader": "5.1.0"
     },
-    "hash": "76239929559a31ed723a76c78e7c2e75d64de46a237e99dd95361916eb0c4d96"
+    "hash": "8a8bb65418f58834b30cd258cd47da52573731720ea8967d4078487cb1253498"
   },
   "dependencies": {
     "lit-element": "2.3.1",
@@ -105,8 +105,7 @@
     "@vaadin/vaadin-tabs": "3.2.0",
     "@vaadin/vaadin-lumo-styles": "1.6.0",
     "@vaadin/vaadin-material-styles": "1.3.2",
-    "open": "^7.2.1",
-    "@vaadin-component-factory/vcf-tooltip": "1.3.13"
+    "open": "^7.2.1"
   },
   "devDependencies": {
     "compression-webpack-plugin": "4.0.1",
diff --git a/src/main/java/edu/kit/typicalc/model/TypeInferenceResult.java b/src/main/java/edu/kit/typicalc/model/TypeInferenceResult.java
index b8e878b..5a1a655 100644
--- a/src/main/java/edu/kit/typicalc/model/TypeInferenceResult.java
+++ b/src/main/java/edu/kit/typicalc/model/TypeInferenceResult.java
@@ -25,11 +25,13 @@ public class TypeInferenceResult {
      *
      * @param substitutions the substitutions to generate the mgu and the final type
      * @param typeVar the type variable belonging to the original lambda term
+     * @throws IllegalStateException if the given list of substitutions contains two substitutions for the same
+     * type variable; or if the calculated mgu contains no substitution for the given type variable
      */
     protected TypeInferenceResult(List<Substitution> substitutions, TypeVariable typeVar) {
         mgu = new ArrayList<>(substitutions);
         findMGU();
-        MGU.sort(Comparator.comparingInt((Substitution o) ->
+        mgu.sort(Comparator.comparingInt((Substitution o) ->
                 o.getVariable().getIndex()).thenComparing(o -> o.getVariable().getKind()));
         finalType = findFinalType(typeVar);
     }
diff --git a/src/main/java/edu/kit/typicalc/model/TypeInfererLet.java b/src/main/java/edu/kit/typicalc/model/TypeInfererLet.java
index 838f471..0241f5b 100644
--- a/src/main/java/edu/kit/typicalc/model/TypeInfererLet.java
+++ b/src/main/java/edu/kit/typicalc/model/TypeInfererLet.java
@@ -36,6 +36,7 @@ public class TypeInfererLet extends TypeInferer {
      */
     public List<Constraint> getLetConstraints() {
         return new ArrayList<>();
+        // TODO
     }
 
 }