diff --git a/src/lagrangian/cfdemParticle/subModels/forceModel/BeetstraDragPoly/BeetstraDragPoly.C b/src/lagrangian/cfdemParticle/subModels/forceModel/BeetstraDragPoly/BeetstraDragPoly.C
index 0d886657..04e12ed9 100644
--- a/src/lagrangian/cfdemParticle/subModels/forceModel/BeetstraDragPoly/BeetstraDragPoly.C
+++ b/src/lagrangian/cfdemParticle/subModels/forceModel/BeetstraDragPoly/BeetstraDragPoly.C
@@ -80,7 +80,7 @@ BeetstraDragPoly::~BeetstraDragPoly()
 
 void BeetstraDragPoly::adaptVoidfraction(double& voidfraction, label cellI) const
 {
-    voidfraction -= alphaSt_()[cellI];
+    if (fines_) voidfraction -= alphaSt_()[cellI];
     if (voidfraction < minVoidfraction_) voidfraction = minVoidfraction_;
 }