diff --git a/src/map/mmc1.c b/src/map/mmc1.c
index 7da9522..ebe86dc 100644
--- a/src/map/mmc1.c
+++ b/src/map/mmc1.c
@@ -263,7 +263,9 @@ static int mmc1_state_read(void* _map, const void* data,
     int base_size = mmc1_state_size(map) - map->chr_ram_lim;
     int size = base_size + mmc1_chr_ram_size(map);
     if (size > data_len) size = data_len;
-    map->chr_ram_lim = data_len - base_size;
+    if (data_len - base_size > map->chr_ram_lim) {
+        map->chr_ram_lim = data_len - base_size;
+    }
     memcpy(&(map->reg_shift), data, size);
 
     mmc1_update_prg(map);