diff --git a/src/cavepacker/shared/BoardState.h b/src/cavepacker/shared/BoardState.h
index a5741539f..05df29fa8 100644
--- a/src/cavepacker/shared/BoardState.h
+++ b/src/cavepacker/shared/BoardState.h
@@ -107,6 +107,8 @@ class BoardState {
 	 * @return @c false if the conversion failed because the index isn't part of the board
 	 */
 	inline bool getColRowFromIndex(int index, int& col, int& row) const {
+		if (index < 0 || index >= _state.size())
+			return false;
 		if (_state[index] == '\0')
 			return false;
 		col = index % _width;