diff --git a/src/main/java/de/studiocode/invui/gui/impl/BaseGUI.java b/src/main/java/de/studiocode/invui/gui/impl/BaseGUI.java
index 869b458..ecc5dfe 100644
--- a/src/main/java/de/studiocode/invui/gui/impl/BaseGUI.java
+++ b/src/main/java/de/studiocode/invui/gui/impl/BaseGUI.java
@@ -97,7 +97,7 @@ public abstract class BaseGUI implements GUI {
                 
                 case DROP_ONE_SLOT:
                 case PICKUP_ONE:
-                    cancel = virtualInventory.setItemAmount(updateReason, slot, -1) != -1;
+                    cancel = virtualInventory.addItemAmount(updateReason, slot, -1) != -1;
                     break;
                 
                 case DROP_ALL_SLOT: