diff --git a/provenience.cabal b/provenience.cabal
--- a/provenience.cabal
+++ b/provenience.cabal
@@ -1,5 +1,5 @@
 name:                provenience
-version:             0.1.2.2
+version:             0.1.2.3
 synopsis:            Computations that automatically track data dependencies
 description:         see README.md
 license:             GPL-3
@@ -19,7 +19,7 @@
   exposed-modules:     Control.Provenience
                      , Data.Representation
                      , Data.Spreadsheet
--- tested against stackage lts-6.35 up to lts-14.22
+-- tested against stackage lts-6.35 up to lts-16.31
   build-depends:       base >= 4.7 && < 5
                      , mtl >= 2.2.1 && <= 2.2.2
                      , fgl >= 5.5.3.1 && < 5.8
diff --git a/src/Control/Provenience.hs b/src/Control/Provenience.hs
--- a/src/Control/Provenience.hs
+++ b/src/Control/Provenience.hs
@@ -328,8 +328,10 @@
             HorizontalRule,
             Div ("",["description"],[]) [description desc],
             Div ("",["valueRendering"],[]) [valueRendering desc]]
-    (n0,n1) = nodeRange (dependencyGraph variables) 
-    in divVars (nodeRange (dependencyGraph variables)) (map renderVariable nodelist)
+    gr = dependencyGraph variables
+    in if noNodes gr > 0
+        then divVars (nodeRange gr) (map renderVariable nodelist)
+        else Null -- nodeRange is a partial function!
 
 -- | When the alternative representation is in terms of spreadsheet rows, 
 -- we can assemble the 'VariableStore' into a spreadheet.