diff --git a/src/GameState.cpp b/src/GameState.cpp
index a316a2e3e0..b75952fe33 100644
--- a/src/GameState.cpp
+++ b/src/GameState.cpp
@@ -2592,8 +2592,12 @@ public:
 	static int AddStageToPlayer( T* p, lua_State *L )				{ p->AddStageToPlayer(Enum::Check<PlayerNumber>(L, 1)); return 0; }
 	static int InsertCoin( T* p, lua_State *L )
 	{
-		int numCoins = lua_tointeger(L, 1);
-		StepMania::InsertCoin(numCoins, false);
+		int numCoins = IArg(1);
+		if (GAMESTATE->m_iCoins + numCoins >= 0)
+			StepMania::InsertCoin(numCoins, false);
+		else
+			luaL_error( L, "Credits may not be negative." );
+
 	}
 	static int InsertCredit( T* p, lua_State *L )
 	{
diff --git a/src/StepMania.cpp b/src/StepMania.cpp
index 5271066b47..f0494f7dcc 100644
--- a/src/StepMania.cpp
+++ b/src/StepMania.cpp
@@ -1252,7 +1252,7 @@ void StepMania::InsertCoin( int iNum, bool bCountInBookkeeping )
 
 	LOG->Trace("%i coins inserted, %i needed to play", GAMESTATE->m_iCoins.Get(), PREFSMAN->m_iCoinsPerCredit.Get() );
 
-	// If inserting coins, play the appropriate sound; if deducting coins, don't.
+	// If inserting coins, play an appropriate sound; if deducting coins, don't play anything.
 	if (iNum > 0)
 	{
 		if( iNumCoinsOld != GAMESTATE->m_iCoins )