diff --git a/src/sampling/sampledSet/array/arraySet.C b/src/sampling/sampledSet/array/arraySet.C
index ca408c105e..66931ea954 100644
--- a/src/sampling/sampledSet/array/arraySet.C
+++ b/src/sampling/sampledSet/array/arraySet.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2018 OpenCFD Ltd.
+    Copyright (C) 2018,2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -56,6 +56,15 @@ void Foam::arraySet::calcSamples
 {
     const meshSearch& queryMesh = searchEngine();
 
+    if (cmptMin(pointsDensity_) < 1)
+    {
+        FatalErrorInFunction << "Illegal specification for pointsDensity "
+            << pointsDensity_
+            << ". It specifies the number of points per coordinate axis"
+            << " so should contain positive integers only."
+            << exit(FatalError);
+    }
+
     const scalar dx = spanBox_.x()/(pointsDensity_.x() + 1);
     const scalar dy = spanBox_.y()/(pointsDensity_.y() + 1);
     const scalar dz = spanBox_.z()/(pointsDensity_.z() + 1);
diff --git a/src/sampling/sampledSet/array/arraySet.H b/src/sampling/sampledSet/array/arraySet.H
index 394403631e..e1772e1221 100644
--- a/src/sampling/sampledSet/array/arraySet.H
+++ b/src/sampling/sampledSet/array/arraySet.H
@@ -39,7 +39,18 @@ Description
         spanBox   | The sample box dimensions (vector)     | yes      |
     \endtable
 
-    The dictionary can also contain an embedded coordinateSystem specification.
+    The dictionary should also contain an embedded (Cartesian) coordinateSystem
+    specification, for example,
+
+    \verbatim
+        origin (-0.05 -0.05 -0.05);
+        rotation
+        {
+            type    axes;
+            e1 (1 0 0);
+            e2 (0 1 0);
+        }
+    \endverbatim
 
 SourceFiles
     arraySet.C