diff --git a/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/AbstractOptimalLStar.java b/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/AbstractOptimalLStar.java
index 12bc8afac..afe211173 100644
--- a/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/AbstractOptimalLStar.java
+++ b/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/AbstractOptimalLStar.java
@@ -35,17 +35,15 @@
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.alphabet.SupportsGrowingAlphabet;
 import net.automatalib.automaton.concept.FiniteRepresentation;
-import net.automatalib.automaton.concept.InputAlphabetHolder;
 import net.automatalib.automaton.concept.SuffixOutput;
 import net.automatalib.word.Word;
 
 abstract class AbstractOptimalLStar<M extends SuffixOutput<I, D>, I, D> implements LearningAlgorithm<M, I, D>,
-                                                                                   InputAlphabetHolder<I>,
                                                                                    SupportsGrowingAlphabet<I>,
                                                                                    Resumable<OptimalLStarState<I, D>>,
                                                                                    FiniteRepresentation {
 
-    private final Alphabet<I> alphabet;
+    final Alphabet<I> alphabet;
     final MembershipOracle<I, D> mqs;
     final MembershipOracle<I, D> ceqs;
 
@@ -109,11 +107,6 @@ public boolean refineHypothesis(DefaultQuery<I, D> counterexample) {
         return refined;
     }
 
-    @Override
-    public Alphabet<I> getInputAlphabet() {
-        return alphabet;
-    }
-
     private void initTable() {
         Word<I> epsilon = Word.epsilon();
         List<D> rowData = initRow(epsilon);
diff --git a/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/OptimalLStarDFA.java b/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/OptimalLStarDFA.java
index e3d4ae235..73df098e7 100644
--- a/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/OptimalLStarDFA.java
+++ b/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/OptimalLStarDFA.java
@@ -53,9 +53,7 @@ boolean symbolInconsistency(Word<I> u1, Word<I> u2, I a) {
 
     @Override
     void automatonFromTable() {
-        Alphabet<I> alphabet = getInputAlphabet();
-
-        this.hypothesis = new CompactDFA<>(alphabet);
+        this.hypothesis = new CompactDFA<>(super.alphabet);
         Map<List<Boolean>, Integer> stateMap = new HashMap<>();
         List<Boolean> rowData = getRow(Word.epsilon());
         Integer q = this.hypothesis.addInitialState(rowData.get(0));
@@ -78,7 +76,7 @@ void automatonFromTable() {
 
             hypStateMap.put(state, sig);
             Word<I> u = getShortPrefixes(sig).get(0);
-            for (I a : alphabet) {
+            for (I a : super.alphabet) {
                 List<Boolean> dstData = getRow(u.append(a));
                 assert dstData != null;
                 Integer dst = stateMap.get(dstData);
diff --git a/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/OptimalLStarMealy.java b/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/OptimalLStarMealy.java
index 6a80fab61..14c589600 100644
--- a/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/OptimalLStarMealy.java
+++ b/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/lstar/OptimalLStarMealy.java
@@ -79,9 +79,7 @@ boolean symbolInconsistency(Word<I> u1, Word<I> u2, I a) {
 
     @Override
     void automatonFromTable() {
-        Alphabet<I> alphabet = getInputAlphabet();
-
-        this.hypothesis = new CompactMealy<>(alphabet);
+        this.hypothesis = new CompactMealy<>(super.alphabet);
         Map<List<Word<O>>, Integer> stateMap = new HashMap<>();
         List<Word<O>> rowData = getRow(Word.epsilon());
         Integer q = this.hypothesis.addInitialState();
@@ -104,7 +102,7 @@ void automatonFromTable() {
 
             hypStateMap.put(state, sig);
             Word<I> u = getShortPrefixes(sig).get(0);
-            for (I a : alphabet) {
+            for (I a : super.alphabet) {
                 Word<I> ua = u.append(a);
                 List<Word<O>> destData = getRow(ua);
                 assert destData != null;
diff --git a/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/ttt/AbstractOptimalTTT.java b/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/ttt/AbstractOptimalTTT.java
index 3de43586f..17959e9d5 100644
--- a/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/ttt/AbstractOptimalTTT.java
+++ b/algorithms/active/oml/src/main/java/de/learnlib/algorithm/oml/ttt/AbstractOptimalTTT.java
@@ -31,12 +31,11 @@
 import de.learnlib.util.MQUtil;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.alphabet.SupportsGrowingAlphabet;
-import net.automatalib.automaton.concept.InputAlphabetHolder;
 import net.automatalib.automaton.concept.SuffixOutput;
 import net.automatalib.word.Word;
 
 public abstract class AbstractOptimalTTT<M extends SuffixOutput<I, D>, I, D>
-        implements LearningAlgorithm<M, I, D>, SupportsGrowingAlphabet<I>, InputAlphabetHolder<I> {
+        implements LearningAlgorithm<M, I, D>, SupportsGrowingAlphabet<I> {
 
     private final MembershipOracle<I, D> ceqs;
     private final Alphabet<I> alphabet;
@@ -115,11 +114,6 @@ public void addAlphabetSymbol(I symbol) {
         }
     }
 
-    @Override
-    public Alphabet<I> getInputAlphabet() {
-        return this.alphabet;
-    }
-
     private void makeConsistent() {
         while (dtree().makeConsistent()) {
             // do nothing ...