diff --git a/src/g_game.c b/src/g_game.c
index 8383782cb..efc96a50f 100644
--- a/src/g_game.c
+++ b/src/g_game.c
@@ -3256,8 +3256,8 @@ void G_AddGametypeConstant(INT16 gtype, const char *newgtconst)
 {
 	size_t r = 0; // read
 	size_t w = 0; // write
-	char *gtconst = Z_Calloc(strlen(newgtconst) + 3, PU_STATIC, NULL);
-	char *tmpconst = Z_Calloc(strlen(newgtconst), PU_STATIC, NULL);
+	char *gtconst = Z_Calloc(strlen(newgtconst) + 4, PU_STATIC, NULL);
+	char *tmpconst = Z_Calloc(strlen(newgtconst) + 1, PU_STATIC, NULL);
 
 	// Copy the gametype name.
 	strcpy(tmpconst, newgtconst);