diff --git a/algo/plot.go b/algo/plot.go
index 50664c2..4aaf45a 100644
--- a/algo/plot.go
+++ b/algo/plot.go
@@ -30,6 +30,10 @@ func plotMeanVals(meanVals []float64, title string, fes int) *plot.Plot {
 	plotter.DefaultFont.Typeface = preferredFont
 	plotter.DefaultLineStyle.Width = vg.Points(2.0)
 
+	if fes != len(meanVals) {
+		log.Fatalf("meanVals - FES mismatch: %d vs %d , bailing\n", fes, len(meanVals))
+	}
+
 	p := plot.New()
 
 	p.Title.Text = "Mean - " + title