diff --git a/src/fileFormats/vtk/vtkUnstructuredReader.C b/src/fileFormats/vtk/vtkUnstructuredReader.C
index 3d80e1ccec6ac05ce02e083b9a386b2f41dc0c94..049f68f89bad0cbfa00c9e1ce727884904d52007 100644
--- a/src/fileFormats/vtk/vtkUnstructuredReader.C
+++ b/src/fileFormats/vtk/vtkUnstructuredReader.C
@@ -704,6 +704,7 @@ void Foam::vtkUnstructuredReader::read(ISstream& inFile)
             labelList faceVerts;
             readBlock(inFile, nNumbers, faceVerts);
             faces_.setSize(nFaces);
+            faceMap_.setSize(nFaces);
             label elemI = 0;
             forAll(faces_, faceI)
             {