diff --git a/src/Boss.cpp b/src/Boss.cpp
index 32abed07..365ec440 100644
--- a/src/Boss.cpp
+++ b/src/Boss.cpp
@@ -35,7 +35,7 @@ void InitBossChar(int code)
 
 void PutBossChar(int fx, int fy)
 {
-	char a = 0;
+	signed char a = 0;
 	int b;
 
 	int side;