diff --git a/src/main/java/us/tastybento/bskyblock/api/panels/builders/PanelBuilder.java b/src/main/java/us/tastybento/bskyblock/api/panels/builders/PanelBuilder.java
index 2c55286cc..7ed59ec74 100644
--- a/src/main/java/us/tastybento/bskyblock/api/panels/builders/PanelBuilder.java
+++ b/src/main/java/us/tastybento/bskyblock/api/panels/builders/PanelBuilder.java
@@ -71,10 +71,13 @@ public class PanelBuilder {
 
     /**
      * Get the next free slot number
-     * @return next slot number
+     * @return next slot number, or -1 in case none has been found.
      */
     public int nextSlot() {
-        return items.isEmpty() ? 0 : items.lastKey() + 1;
+        for (int i = 0 ; i < (size == 0 ? 54 : size) ; i++) {
+            if (!slotOccupied(i)) return i;
+        }
+        return -1;
     }
 
     /**