diff --git a/NCPCompatBukkit/src/main/java/fr/neatmonster/nocheatplus/compat/bukkit/MCAccessBukkit.java b/NCPCompatBukkit/src/main/java/fr/neatmonster/nocheatplus/compat/bukkit/MCAccessBukkit.java
index 19045d69..7cf73218 100644
--- a/NCPCompatBukkit/src/main/java/fr/neatmonster/nocheatplus/compat/bukkit/MCAccessBukkit.java
+++ b/NCPCompatBukkit/src/main/java/fr/neatmonster/nocheatplus/compat/bukkit/MCAccessBukkit.java
@@ -47,10 +47,10 @@ public class MCAccessBukkit extends MCAccessBukkitBase implements BlockPropertie
             if (!mat.isBlock()) {
                 continue;
             }
-            if (fullBlocks.contains(mat)) {
+            else if (fullBlocks.contains(mat)) {
                 continue;
             }
-            if (!mat.isOccluding() || !mat.isSolid() || mat.isTransparent()) {
+            else if (guessItchyBlock(mat)) {
                 // Uncertain bounding-box, allow passing through.
                 long flags = BlockProperties.F_IGN_PASSABLE;
                 if ((BlockProperties.isSolid(mat) || BlockProperties.isGround(mat)) && !BlockProperties.isLiquid(mat)) {
diff --git a/NCPCompatBukkit/src/main/java/fr/neatmonster/nocheatplus/compat/bukkit/MCAccessBukkitBase.java b/NCPCompatBukkit/src/main/java/fr/neatmonster/nocheatplus/compat/bukkit/MCAccessBukkitBase.java
index 94ed7ee0..ae0096de 100644
--- a/NCPCompatBukkit/src/main/java/fr/neatmonster/nocheatplus/compat/bukkit/MCAccessBukkitBase.java
+++ b/NCPCompatBukkit/src/main/java/fr/neatmonster/nocheatplus/compat/bukkit/MCAccessBukkitBase.java
@@ -40,14 +40,26 @@ public class MCAccessBukkitBase implements MCAccess {
     // private AlmostBoolean entityPlayerAvailable = AlmostBoolean.MAYBE;
     protected final boolean bukkitHasGetHeightAndGetWidth;
 
+    private boolean guessItchyBlockPre1_13(final Material mat) {
+        return !mat.isOccluding() || !mat.isSolid() || mat.isTransparent();
+    }
+
+    protected boolean guessItchyBlock(final Material mat) {
+        // TODO: Use working route.
+        return guessItchyBlockPre1_13(mat);
+    }
+
+    private void testItchyBlock() {
+        // TODO: Route to what works.
+        guessItchyBlockPre1_13(Material.AIR);
+    }
+
     /**
      * Constructor to let it fail.
      */
     public MCAccessBukkitBase() {
         // TODO: Add more that might fail if not supported ?
-        Material.AIR.isSolid();
-        Material.AIR.isOccluding();
-        Material.AIR.isTransparent();
+        testItchyBlock();
         // TODO: Deactivate checks that might not work. => MCAccess should have availability method, NCP deactivates check on base of that.
         // TODO: Move getHeight and the like to EntityAccessXY.
         bukkitHasGetHeightAndGetWidth = ReflectionUtil.getMethodNoArgs(Entity.class, "getHeight", double.class) != null