diff --git a/src/lagrangian/intermediate/parcels/Templates/ReactingParcel/ReactingParcelIO.C b/src/lagrangian/intermediate/parcels/Templates/ReactingParcel/ReactingParcelIO.C
index 49a0ef0cf958ba24d58bf7b7fd7430f6841436e2..62d300ea0647189cf75a346892ad99fc5626ef16 100644
--- a/src/lagrangian/intermediate/parcels/Templates/ReactingParcel/ReactingParcelIO.C
+++ b/src/lagrangian/intermediate/parcels/Templates/ReactingParcel/ReactingParcelIO.C
@@ -182,7 +182,7 @@ void Foam::ReactingParcel<ParcelType>::writeFields
         label i = 0;
         for (const ReactingParcel<ParcelType>& p : c)
         {
-            mass0[i++] = p.mass0_;
+            mass0[i] = p.mass0_;
 
             ++i;
         }