diff --git a/core/src/main/java/net/automatalib/automata/base/compact/AbstractCompactDeterministic.java b/core/src/main/java/net/automatalib/automata/base/compact/AbstractCompactDeterministic.java
index <HASH>..<HASH> 100644
--- a/core/src/main/java/net/automatalib/automata/base/compact/AbstractCompactDeterministic.java
+++ b/core/src/main/java/net/automatalib/automata/base/compact/AbstractCompactDeterministic.java
@@ -129,7 +129,7 @@ public abstract class AbstractCompactDeterministic<I, T, SP, TP> extends Abstrac
 
     @Override
     public int addIntInitialState(@Nullable SP property) {
-        this.initial = addIntState(property);
+        setInitial(addIntState(property), true);
         return this.initial;
     }
fix adding mutliple initial states on compact determistics

previously, adding a (second) initial state on automata extending from `AbstractCompactDeterministic` silently overrode the previous initial state, if existent. Now, if this operation would introduce non-determinism, an exception is thrown as expected.