diff --git a/src/gamestate.cpp b/src/gamestate.cpp
index 9fe3e6e..999d758 100644
--- a/src/gamestate.cpp
+++ b/src/gamestate.cpp
@@ -452,7 +452,7 @@ QString GameState::generateStateHash() const {
             stateHash += ",";
         }
 
-        if (stateHash.last(1) != "|")
+        if (stateHash.length() > 0 && stateHash.last(1) != "|")
             stateHash.removeLast();
         stateHash += "|";
     }
@@ -464,7 +464,7 @@ QString GameState::generateStateHash() const {
         for (const PlayingCard* card : foundationPile) {
             stateHash += QString::number(card->value()) + "." + QString::number(card->suit()) + ",";
         }
-        if (stateHash.last(1) != "|")
+        if (stateHash.length() > 0 && stateHash.last(1) != "|")
             stateHash.removeLast();
         stateHash += "|";
     }
@@ -588,7 +588,8 @@ bool GameState::isColumnMoveValid(const PlayingCard& cardToMove, int columnId) c
     const PlayingCard& columnCard = *columnStack.last()->card();
 
     // The card's value must be one less than the card in the column
-    if (cardToMove.value() != static_cast<PlayingCard::Value>(static_cast<int>(columnCard.value() - 1)))
+    const int reqValue = static_cast<int>(columnCard.value() - 1);
+    if (reqValue < 0 || cardToMove.value() != static_cast<PlayingCard::Value>(reqValue))
         return false;
 
     // The card must be of opposite color