diff --git a/alib/src/automaton/TM/TM.cpp b/alib/src/automaton/TM/TM.cpp
index 02f80f61674869d8f314bf311a0bc7c1e778e0ca..edb73c66b5e7d312ac29d2aabe6ba192abca4270 100644
--- a/alib/src/automaton/TM/TM.cpp
+++ b/alib/src/automaton/TM/TM.cpp
@@ -95,8 +95,10 @@ void TM::addTransition(const TransitionTM& transition) {
 		throw AutomatonException("State \"" + transition.getFrom().getName() + "\" doesn't exist.");
 	}
 
-	if (tapeAlphabet.find(transition.getInput()) == tapeAlphabet.end()) {
-		throw AutomatonException("Tape symbol \"" + transition.getInput().getSymbol() + "\" doesn't exist.");
+	if (transition.getInput().getSymbol() != "") {
+		if (tapeAlphabet.find(transition.getInput()) == tapeAlphabet.end()) {
+			throw AutomatonException("Tape symbol \"" + transition.getInput().getSymbol() + "\" doesn't exist.");
+		}
 	}
 
 	if (states.find(transition.getTo()) == states.end()) {