diff --git a/instat/ucrCalculator.vb b/instat/ucrCalculator.vb
index c399fb9c7f0..a340a2cb56b 100644
--- a/instat/ucrCalculator.vb
+++ b/instat/ucrCalculator.vb
@@ -63,6 +63,7 @@ Public Class ucrCalculator
         cmdAll.Enabled = False
         cmdIsTrue.Enabled = False
         cmdIsFalse.Enabled = False
+        cmdConcat.Enabled = False
         bControlsInitialised = True
         ttCalculator.SetToolTip(cmdRound, "round(x) to round to whole numbers, round(x,2) to round to 2 decimal places, round(x,-2) to round to the nearest 100")
         ttCalculator.SetToolTip(cmdSiginf, "signif(x,3) to round to 3 significant figures")