Index: /issm/trunk-jpl/src/m/classes/stressbalance.py
===================================================================
--- /issm/trunk-jpl/src/m/classes/stressbalance.py	(revision 24290)
+++ /issm/trunk-jpl/src/m/classes/stressbalance.py	(revision 24291)
@@ -134,5 +134,5 @@
         md = checkfield(md, 'fieldname', 'stressbalance.loadingforce', 'size', [md.mesh.numberofvertices, 3])
         md = checkfield(md, 'fieldname', 'stressbalance.requested_outputs', 'stringrow', 1)
-        if not np.any(np.isnan(self.vertex_pairing)):
+        if not np.any(np.isnan(self.vertex_pairing)) and len(self.vertex_pairing)>0:
             md = checkfield(md, 'fieldname', 'stressbalance.vertex_pairing', '>', 0)
         #singular solution