diff --git a/library/DFHackAPI.cpp b/library/DFHackAPI.cpp
index fbd659f3c5..07a53f32e3 100644
--- a/library/DFHackAPI.cpp
+++ b/library/DFHackAPI.cpp
@@ -220,7 +220,7 @@ bool API::InitMap()
     /*
      * --> SHM initialization (if possible) <--
      */
-    g_pProcess->getModuleIndex("Maps",2,d->maps_module);
+    g_pProcess->getModuleIndex("Maps",3,d->maps_module);
     
     if(d->maps_module)
     {
@@ -351,7 +351,7 @@ bool API::ReadTileTypes (uint32_t x, uint32_t y, uint32_t z, tiletypes40d *buffe
     uint32_t addr = d->block[x*d->y_block_count*d->z_block_count + y*d->z_block_count + z];
     if (addr)
     {
-        g_pProcess->read (addr + d->tile_type_offset, 256 * sizeof (uint16_t), (uint8_t *) buffer);
+        g_pProcess->read (addr + d->tile_type_offset, sizeof (tiletypes40d), (uint8_t *) buffer);
         return true;
     }
     return false;
@@ -413,7 +413,7 @@ bool API::ReadDesignations (uint32_t x, uint32_t y, uint32_t z, designations40d
     uint32_t addr = d->block[x*d->y_block_count*d->z_block_count + y*d->z_block_count + z];
     if (addr)
     {
-        g_pProcess->read (addr + d->designation_offset, 256 * sizeof (uint32_t), (uint8_t *) buffer);
+        g_pProcess->read (addr + d->designation_offset, sizeof (designations40d), (uint8_t *) buffer);
         return true;
     }
     return false;
@@ -426,7 +426,7 @@ bool API::ReadOccupancy (uint32_t x, uint32_t y, uint32_t z, occupancies40d *buf
     uint32_t addr = d->block[x*d->y_block_count*d->z_block_count + y*d->z_block_count + z];
     if (addr)
     {
-        g_pProcess->read (addr + d->occupancy_offset, 256 * sizeof (uint32_t), (uint8_t *) buffer);
+        g_pProcess->read (addr + d->occupancy_offset, sizeof (occupancies40d), (uint8_t *) buffer);
         return true;
     }
     return false;
@@ -439,7 +439,7 @@ bool API::WriteTileTypes (uint32_t x, uint32_t y, uint32_t z, tiletypes40d *buff
     uint32_t addr = d->block[x*d->y_block_count*d->z_block_count + y*d->z_block_count + z];
     if (addr)
     {
-        g_pProcess->write (addr + d->tile_type_offset, 256 * sizeof (uint16_t), (uint8_t *) buffer);
+        g_pProcess->write (addr + d->tile_type_offset, sizeof (tiletypes40d), (uint8_t *) buffer);
         return true;
     }
     return false;
@@ -457,7 +457,7 @@ bool API::WriteDesignations (uint32_t x, uint32_t y, uint32_t z, designations40d
     uint32_t addr = d->block[x*d->y_block_count*d->z_block_count + y*d->z_block_count + z];
     if (addr)
     {
-        g_pProcess->write (addr + d->designation_offset, 256 * sizeof (uint32_t), (uint8_t *) buffer);
+        g_pProcess->write (addr + d->designation_offset, sizeof (designations40d), (uint8_t *) buffer);
         return true;
     }
     return false;
@@ -469,7 +469,7 @@ bool API::WriteOccupancy (uint32_t x, uint32_t y, uint32_t z, occupancies40d *bu
     uint32_t addr = d->block[x*d->y_block_count*d->z_block_count + y*d->z_block_count + z];
     if (addr)
     {
-        g_pProcess->write (addr + d->occupancy_offset, 256 * sizeof (uint32_t), (uint8_t *) buffer);
+        g_pProcess->write (addr + d->occupancy_offset, sizeof (occupancies40d), (uint8_t *) buffer);
         return true;
     }
     return false;
@@ -483,7 +483,7 @@ bool API::ReadRegionOffsets (uint32_t x, uint32_t y, uint32_t z, biome_indices40
     uint32_t addr = d->block[x*d->y_block_count*d->z_block_count + y*d->z_block_count + z];
     if (addr)
     {
-        g_pProcess->read (addr + d->biome_stuffs, 16 * sizeof (uint8_t), (uint8_t *) buffer);
+        g_pProcess->read (addr + d->biome_stuffs, sizeof (biome_indices40d), (uint8_t *) buffer);
         return true;
     }
     return false;
diff --git a/library/DFTypes.h b/library/DFTypes.h
index 5ef92670cc..40b5c57cc2 100644
--- a/library/DFTypes.h
+++ b/library/DFTypes.h
@@ -853,7 +853,7 @@ union t_blockflags
 typedef int16_t tiletypes40d [16][16];
 typedef DFHack::t_designation designations40d [16][16];
 typedef DFHack::t_occupancy occupancies40d [16][16];
-typedef uint8_t biome_indices40d [8];
+typedef uint8_t biome_indices40d [16];
 
 typedef struct
 {
diff --git a/shmserver/mod-maps.h b/shmserver/mod-maps.h
index af6b8f48e3..bd1ad94a9c 100644
--- a/shmserver/mod-maps.h
+++ b/shmserver/mod-maps.h
@@ -33,7 +33,7 @@ namespace DFHack
     namespace Maps
     {
 
-#define MAPS_VERSION 2
+#define MAPS_VERSION 3
 typedef struct
 {
     uint32_t map_offset;// = d->offset_descriptor->getAddress ("map_data");