diff --git a/hrw.go b/hrw.go
index f946dda..c1a990f 100644
--- a/hrw.go
+++ b/hrw.go
@@ -5,6 +5,7 @@ package hrw
 import (
 	"encoding/binary"
 	"errors"
+	"math"
 	"reflect"
 	"sort"
 
@@ -293,7 +294,7 @@ func prepareRule(slice interface{}) []uint64 {
 // ValidateWeights checks if weights are normalized between 0.0 and 1.0
 func ValidateWeights(weights []float64) error {
 	for i := range weights {
-		if weights[i] > NormalizedMaxWeight || weights[i] < NormalizedMinWeight {
+		if math.IsNaN(weights[i]) || weights[i] > NormalizedMaxWeight || weights[i] < NormalizedMinWeight {
 			return errors.New("weights are not normalized")
 		}
 	}
diff --git a/hrw_test.go b/hrw_test.go
index 389d88d..fb7a34d 100644
--- a/hrw_test.go
+++ b/hrw_test.go
@@ -76,6 +76,9 @@ func TestValidateWeights(t *testing.T) {
 	weights := []float64{10, 10, 10, 2, 2, 2}
 	err := ValidateWeights(weights)
 	require.Error(t, err)
+	weights = []float64{math.NaN(), 1, 1, 0.2, 0.2, 0.2}
+	err = ValidateWeights(weights)
+	require.Error(t, err)
 	weights = []float64{1, 1, 1, 0.2, 0.2, 0.2}
 	err = ValidateWeights(weights)
 	require.NoError(t, err)