diff --git a/weed/util/bytes.go b/weed/util/bytes.go
index 4e9ce1d15..b3217a195 100644
--- a/weed/util/bytes.go
+++ b/weed/util/bytes.go
@@ -13,6 +13,8 @@ import (
 	"unicode"
 )
 
+var randomRead = rand.Read
+
 // BytesToHumanReadable returns the converted human readable representation of the bytes.
 func BytesToHumanReadable(b uint64) string {
 	const unit = 1024
@@ -156,10 +158,12 @@ func RandomInt32() int32 {
 	return int32(BytesToUint32(buf))
 }
 
-func RandomUint64() int32 {
+func RandomUint64() uint64 {
 	buf := make([]byte, 8)
-	rand.Read(buf)
-	return int32(BytesToUint64(buf))
+	if _, err := randomRead(buf); err != nil {
+		panic(err)
+	}
+	return BytesToUint64(buf)
 }
 
 func RandomBytes(byteCount int) []byte {
diff --git a/weed/util/bytes_test.go b/weed/util/bytes_test.go
index d9269cadb..31c7af40c 100644
--- a/weed/util/bytes_test.go
+++ b/weed/util/bytes_test.go
@@ -1,6 +1,45 @@
 package util
 
-import "testing"
+import (
+	"errors"
+	"testing"
+)
+
+func TestRandomUint64ReturnsFullRandomValue(t *testing.T) {
+	useRandomRead(t, func(p []byte) (int, error) {
+		copy(p, []byte{0x80, 0, 0, 0, 0, 0, 0, 1})
+		return len(p), nil
+	})
+
+	const want uint64 = 0x8000000000000001
+	if got := RandomUint64(); got != want {
+		t.Fatalf("RandomUint64() = %d, want %d", got, want)
+	}
+}
+
+func TestRandomUint64PanicsOnRandomReadError(t *testing.T) {
+	useRandomRead(t, func([]byte) (int, error) {
+		return 0, errors.New("random read failed")
+	})
+
+	defer func() {
+		if recover() == nil {
+			t.Fatal("RandomUint64() did not panic on random read error")
+		}
+	}()
+
+	RandomUint64()
+}
+
+func useRandomRead(t *testing.T, read func([]byte) (int, error)) {
+	t.Helper()
+
+	original := randomRead
+	randomRead = read
+	t.Cleanup(func() {
+		randomRead = original
+	})
+}
 
 func TestByteParsing(t *testing.T) {
 	tests := []struct {