diff --git a/overviewer_core/src/iterate.c b/overviewer_core/src/iterate.c
index 450815b..041f0b4 100644
--- a/overviewer_core/src/iterate.c
+++ b/overviewer_core/src/iterate.c
@@ -284,14 +284,15 @@ generate_pseudo_data(RenderState *state, unsigned char ancilData) {
 
         return final_data;
 
-    /* portal, iron bars and glass panes
-     * Note: iron bars and glass panes "stick" to other blocks, but
-     * at the moment of writing this is not clear which ones stick and
-     * which others no, so for the moment stick only with himself.
-     * This is a TODO!
-     */
-    } else if ((state->block == 90) || (state->block == 101) ||
-               (state->block == 102) || (state->block == 113)) {
+    } else if ((state->block == 101) || (state->block == 102)) {
+        /* iron bars and glass panes:
+         * they seem to stick to almost everything but air, but
+         * not sure yet! Still a TODO! */
+        /* return check adjacent blocks with air, bit inverted */
+        return check_adjacent_blocks(state, x, y, z, 0) ^ 0x0f;
+
+    } else if ((state->block == 90) || (state->block == 113)) {
+        /* portal and nether brick fences */
         return check_adjacent_blocks(state, x, y, z, state->block);
     }