diff --git a/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.C b/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.C
index cd395a5bc6..c9d50b8930 100644
--- a/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.C
+++ b/src/finiteVolume/fields/fvPatchFields/derived/waveSurfacePressure/waveSurfacePressureFvPatchScalarField.C
@@ -187,7 +187,7 @@ void Foam::waveSurfacePressureFvPatchScalarField::updateCoeffs()
 
         operator==(-g.value() & zetap);
     }
-    else if (phi.dimensions() = dimDensity*dimVelocity*dimArea)
+    else if (phi.dimensions() == dimDensity*dimVelocity*dimArea)
     {
         const scalarField& rhop =
             patch().lookupPatchField<volScalarField, scalar>(rhoName_);