diff --git a/overviewer_core/src/overviewer.h b/overviewer_core/src/overviewer.h
index 76a7830..1d9b7f5 100644
--- a/overviewer_core/src/overviewer.h
+++ b/overviewer_core/src/overviewer.h
@@ -33,7 +33,7 @@
 
 // increment this value if you've made a change to the c extesion
 // and want to force users to rebuild
-#define OVERVIEWER_EXTENSION_VERSION 60
+#define OVERVIEWER_EXTENSION_VERSION 61
 
 /* Python PIL, and numpy headers */
 #include <Python.h>
diff --git a/overviewer_core/src/primitives/base.c b/overviewer_core/src/primitives/base.c
index cf8dbae..a3fda71 100644
--- a/overviewer_core/src/primitives/base.c
+++ b/overviewer_core/src/primitives/base.c
@@ -77,7 +77,7 @@ base_draw(void *data, RenderState *state, PyObject *src, PyObject *mask, PyObjec
     PrimitiveBase *self = (PrimitiveBase *)data;
 
     /* in order to detect top parts of doublePlant grass & ferns */
-    unsigned char below_block = get_data(state, BLOCKS, state->x, state->y-1, state->z);
+    unsigned short below_block = get_data(state, BLOCKS, state->x, state->y-1, state->z);
     unsigned char below_data = get_data(state, DATA, state->x, state->y-1, state->z);
 
     /* draw the block! */
diff --git a/overviewer_core/src/primitives/overlay-structure.c b/overviewer_core/src/primitives/overlay-structure.c
index bc4a7cf..2c40607 100644
--- a/overviewer_core/src/primitives/overlay-structure.c
+++ b/overviewer_core/src/primitives/overlay-structure.c
@@ -29,7 +29,7 @@ typedef struct {
 
 struct Condition{
     int relx, rely, relz;
-    unsigned char block;
+    unsigned short block;
 };
 
 struct Color {