diff --git a/src/sampling/sampledSurface/isoSurface/sampledIsoSurfaceTopo.C b/src/sampling/sampledSurface/isoSurface/sampledIsoSurfaceTopo.C
index 0e9cf4ed11..058cf05fcf 100644
--- a/src/sampling/sampledSurface/isoSurface/sampledIsoSurfaceTopo.C
+++ b/src/sampling/sampledSurface/isoSurface/sampledIsoSurfaceTopo.C
@@ -180,10 +180,10 @@ Foam::sampledIsoSurfaceTopo::sampledIsoSurfaceTopo
     prevTimeIndex_(-1),
     meshCells_()
 {
-    if (triangulate_ && filter_ != isoSurfaceBase::filterType::NONE)
+    if (triangulate_ && filter_ == isoSurfaceBase::filterType::NONE)
     {
         FatalIOErrorInFunction(dict)
-            << "Cannot both use triangulate and regularise" << nl
+            << "Cannot triangulate without a regularise filter" << nl
             << exit(FatalIOError);
     }
 }
diff --git a/src/sampling/sampledSurface/isoSurface/sampledIsoSurfaceTopo.H b/src/sampling/sampledSurface/isoSurface/sampledIsoSurfaceTopo.H
index 3f52202acb..5f75e631d1 100644
--- a/src/sampling/sampledSurface/isoSurface/sampledIsoSurfaceTopo.H
+++ b/src/sampling/sampledSurface/isoSurface/sampledIsoSurfaceTopo.H
@@ -102,7 +102,7 @@ class sampledIsoSurfaceTopo
         //- Filtering for iso-surface triangles
         const isoSurfaceBase::filterType filter_;
 
-        //- Whether to triangulate
+        //- Whether to triangulate (after filtering)
         const bool triangulate_;