diff --git a/p2/stats/stats.go b/p2/stats/stats.go
index 149576b..67ce6a3 100644
--- a/p2/stats/stats.go
+++ b/p2/stats/stats.go
@@ -66,7 +66,7 @@ func AutocorrelateMP(f []float64, maxShift float64) []float64 {
 func MutCorrelate(f1, f2 []float64, maxShift float64) ([]float64, error) {
 	fLen := len(f1)
 	if fLen != len(f2) {
-		return []float64{}, errors.New("arrays passed are of different lengths")
+		return nil, errors.New("arrays passed are of different lengths")
 	}
 
 	m := float64(fLen) * maxShift