diff --git a/db/merge.go b/db/merge.go
index 1a01d84d..4fede17b 100644
--- a/db/merge.go
+++ b/db/merge.go
@@ -271,6 +271,8 @@ func (d *document) mrgFld(ctx context.Context) (err error) {
 
 		err = d.current.Walk(func(key string, val interface{}) (err error) {
 
+			vars := data.New()
+
 			var old = d.initial.Get(key).Data()
 
 			// Ensure the field is the correct type
@@ -281,7 +283,8 @@ func (d *document) mrgFld(ctx context.Context) (err error) {
 				}
 			}
 
-			vars := data.New()
+			// Reset the variables
+
 			vars.Set(val, varKeyValue)
 			vars.Set(val, varKeyAfter)
 			vars.Set(old, varKeyBefore)
@@ -295,6 +298,13 @@ func (d *document) mrgFld(ctx context.Context) (err error) {
 				}
 			}
 
+			// Reset the variables
+
+			vars.Set(val, varKeyValue)
+			vars.Set(val, varKeyAfter)
+			vars.Set(old, varKeyBefore)
+			ctx = context.WithValue(ctx, ctxKeySubs, vars)
+
 			// We are checking the value of the field
 
 			if fd.Assert != nil {