diff --git a/src/finiteArea/fields/faPatchFields/constraint/processor/processorFaPatchScalarField.C b/src/finiteArea/fields/faPatchFields/constraint/processor/processorFaPatchScalarField.C
index fe5b4dc27..3d50502a1 100644
--- a/src/finiteArea/fields/faPatchFields/constraint/processor/processorFaPatchScalarField.C
+++ b/src/finiteArea/fields/faPatchFields/constraint/processor/processorFaPatchScalarField.C
@@ -83,7 +83,7 @@ void processorFaPatchField<scalar>::updateInterfaceMatrix
     {
         forAll(edgeFaces, facei)
         {
-            result[edgeFaces[facei]] -= coeffs[facei]*pnf[facei];
+            result[edgeFaces[facei]] += coeffs[facei]*pnf[facei];
         }
     }
     else