diff --git a/src/keyboard_input/input_parser.cpp b/src/keyboard_input/input_parser.cpp
index da4692f..fce3d02 100644
--- a/src/keyboard_input/input_parser.cpp
+++ b/src/keyboard_input/input_parser.cpp
@@ -61,7 +61,7 @@ std::vector<Token> ParseKeyboardInputsToTokens( const std::string inputs )
 {
     std::vector<Token> tokens{};
 
-    for ( auto ch = inputs.begin(); ch != inputs.end(); ++ch )
+    for ( auto ch = inputs.begin(), end = inputs.end(); ch != end; ++ch )
     {
         if ( const auto c = getNumberOrLetter( *ch ); c.has_value() )
         {
@@ -84,6 +84,10 @@ std::vector<Token> ParseKeyboardInputsToTokens( const std::string inputs )
         if ( *ch == 'F' )
         {
             ++ch;
+            if ( ch == end )
+            {
+                break;
+            }
             const auto token = getFunctionNumber( *ch );
             if ( token.has_value() )
             {
diff --git a/test/keyboard_input/tst_parsertest.cpp b/test/keyboard_input/tst_parsertest.cpp
index 7c73dce..ce6215f 100644
--- a/test/keyboard_input/tst_parsertest.cpp
+++ b/test/keyboard_input/tst_parsertest.cpp
@@ -24,6 +24,8 @@ private slots:
     void Modifiers();
 
     void functionKeys();
+
+    void shouldExitEarlyFunctionKey();
 };
 
 const std::string alphabet = "abcdefghijklmnopqrstuvxyz";
@@ -164,6 +166,25 @@ void ParserTest::functionKeys()
     QVERIFY( t == e );
 }
 
+void ParserTest::shouldExitEarlyFunctionKey()
+{
+    auto t = ParseKeyboardInputsToTokens( "asF" );
+    auto e = std::vector<Token>( { Token::KEY_a, Token::KEY_s } );
+    QVERIFY( t == e );
+
+    t = ParseKeyboardInputsToTokens( "asFs" );
+    e = std::vector<Token>( { Token::KEY_a, Token::KEY_s } );
+    QVERIFY( t == e );
+
+    t = ParseKeyboardInputsToTokens( "F" );
+    e = std::vector<Token>( {} );
+    QVERIFY( t == e );
+
+    t = ParseKeyboardInputsToTokens( "Fsdfg" );
+    e = std::vector<Token>( {} );
+    QVERIFY( t == e );
+}
+
 QTEST_APPLESS_MAIN( ParserTest )
 
 #include "tst_parsertest.moc"