diff --git a/lib/autotune-prep/categorize.js b/lib/autotune-prep/categorize.js
index 5ebb8fde5..4166bb5d0 100644
--- a/lib/autotune-prep/categorize.js
+++ b/lib/autotune-prep/categorize.js
@@ -221,7 +221,7 @@ function categorizeBGDatums(opts) {
         glucoseDatum.BGI = BGI;
         // calculating deviation
         var deviation = avgDelta-BGI;
-        dev5m = delta-BGI;
+        var dev5m = delta-BGI;
         //console.error(deviation,avgDelta,BG,bucketedData[i].glucose);
 
         // set positive deviations to zero if BG is below 80