diff --git a/src/meshTools/searchableSurface/distributedTriSurfaceMesh.C b/src/meshTools/searchableSurface/distributedTriSurfaceMesh.C
index a42408e9bc..adfe29401e 100644
--- a/src/meshTools/searchableSurface/distributedTriSurfaceMesh.C
+++ b/src/meshTools/searchableSurface/distributedTriSurfaceMesh.C
@@ -2192,9 +2192,10 @@ bool Foam::distributedTriSurfaceMesh::writeObject
     // Make sure dictionary goes to same directory as surface
     const_cast<fileName&>(dict_.instance()) = searchableSurface::instance();
 
+    // Dictionary needs to be written in ascii - binary output not supported.
     return
         triSurfaceMesh::writeObject(fmt, ver, cmp)
-     && dict_.writeObject(fmt, ver, cmp);
+     && dict_.writeObject(IOstream::ASCII, ver, cmp);
 }