diff --git a/overviewer_core/src/iterate.c b/overviewer_core/src/iterate.c
index c6c46a1..47e175b 100644
--- a/overviewer_core/src/iterate.c
+++ b/overviewer_core/src/iterate.c
@@ -20,6 +20,7 @@
 static PyObject *textures = NULL;
 static PyObject *chunk_mod = NULL;
 static PyObject *blockmap = NULL;
+static PyObject *known_blocks = NULL;
 static PyObject *transparent_blocks = NULL;
 
 PyObject *init_chunk_render(PyObject *self, PyObject *args) {
@@ -45,6 +46,9 @@ PyObject *init_chunk_render(PyObject *self, PyObject *args) {
     blockmap = PyObject_GetAttrString(textures, "blockmap");
     if (!blockmap)
         return NULL;
+    known_blocks = PyObject_GetAttrString(textures, "known_blocks");
+    if (!known_blocks)
+        return NULL;
     transparent_blocks = PyObject_GetAttrString(textures, "transparent_blocks");
     if (!transparent_blocks)
         return NULL;
@@ -56,6 +60,10 @@ int
 is_transparent(unsigned char b) {
     PyObject *block = PyInt_FromLong(b);
     int ret = PySequence_Contains(transparent_blocks, block);
+    if (!ret)
+    {
+        ret = !(PySequence_Contains(known_blocks, block));
+    }
     Py_DECREF(block);
     return ret;
 
diff --git a/overviewer_core/textures.py b/overviewer_core/textures.py
index 2bbbbb4..39d4739 100644
--- a/overviewer_core/textures.py
+++ b/overviewer_core/textures.py
@@ -546,7 +546,8 @@ blockmap_generators = {}
 blockmap = {}
 biome_grass_texture = None
 
-transparent_blocks = set([0,])
+known_blocks = set()
+transparent_blocks = set()
 solid_blocks = set()
 fluid_blocks = set()
 nospawn_blocks = set()
@@ -579,6 +580,7 @@ def material(blockid=[], data=[0], **kwargs):
         
         for block in blockid:
             # set the property sets appropriately
+            known_blocks.update([block])
             for prop in properties:
                 try:
                     if block in kwargs.get(prop, []):