diff --git a/api/orders/setLineItem.cfm b/api/orders/setLineItem.cfm
index cf2ff2d..5a0223a 100644
--- a/api/orders/setLineItem.cfm
+++ b/api/orders/setLineItem.cfm
@@ -347,11 +347,11 @@
       <cfset apiAbort({ "OK": false, "ERROR": "bad_quantity", "MESSAGE": "Root line items require Quantity > 0.", "DETAIL": "" })>
     </cfif>
   <cfelse>
-    <!--- Modifier quantity is implicitly tied => force 1 when selecting --->
+    <!--- Modifier quantity is implicitly tied => force 1 when selecting, 0 when deselecting --->
     <cfif IsSelected>
       <cfset Quantity = 1>
     <cfelse>
-      <cfset Quantity = 1>
+      <cfset Quantity = 0>
     </cfif>
 
     <!--- Check if this is an exclusive selection group (max = 1) --->