diff --git a/altsrc/flag.go b/altsrc/flag.go
index 725f58f843..4b1c95d5fb 100644
--- a/altsrc/flag.go
+++ b/altsrc/flag.go
@@ -2,7 +2,6 @@ package altsrc
 
 import (
 	"fmt"
-	"log"
 	"path/filepath"
 	"strconv"
 	"syscall"
@@ -125,7 +124,6 @@ func (f *Int64SliceFlag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourc
 	if f.set != nil && !cCtx.IsSet(f.Name) && !isEnvVarSet(f.EnvVars) && isc.isSet(f.Int64SliceFlag.Name) {
 		value, err := isc.Int64Slice(f.Int64SliceFlag.Name)
 		if err != nil {
-			log.Print(err)
 			return err
 		}
 		if value != nil {
diff --git a/altsrc/json_command_test.go b/altsrc/json_command_test.go
index bd0022b1cd..f6f49890ba 100644
--- a/altsrc/json_command_test.go
+++ b/altsrc/json_command_test.go
@@ -12,6 +12,12 @@ import (
 const (
 	fileName   = "current.json"
 	simpleJSON = `{"test": 15}`
+	sliceJSON  = `
+	{
+		"test1" : [214767949494, 23333495956],
+		"test2" : [1,2,3,-566]
+	}
+	`
 	nestedJSON = `{"top": {"test": 15}}`
 )
 
@@ -46,6 +52,41 @@ func TestCommandJSONFileTest(t *testing.T) {
 	expect(t, err, nil)
 }
 
+func TestCommandJSONFileTestSlices(t *testing.T) {
+	cleanup := writeTempFile(t, fileName, sliceJSON)
+	defer cleanup()
+
+	app := &cli.App{}
+	set := flag.NewFlagSet("test", 0)
+	test := []string{"test-cmd", "--load", fileName}
+	_ = set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) error {
+			val1 := c.Uint64Slice("test1")
+			expect(t, val1, []uint64{214767949494, 23333495956})
+
+			val2 := c.Int64Slice("test2")
+			expect(t, val2, []int64{1, 2, 3, -566})
+			return nil
+		},
+		Flags: []cli.Flag{
+			NewUint64SliceFlag(&cli.Uint64SliceFlag{Name: "test1"}),
+			NewInt64SliceFlag(&cli.Int64SliceFlag{Name: "test2"}),
+			&cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewJSONSourceFromFlagFunc("load"))
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
 func TestCommandJSONFileTestGlobalEnvVarWins(t *testing.T) {
 	cleanup := writeTempFile(t, fileName, simpleJSON)
 	defer cleanup()
diff --git a/altsrc/json_source_context.go b/altsrc/json_source_context.go
index 5c30349053..5ce3121e31 100644
--- a/altsrc/json_source_context.go
+++ b/altsrc/json_source_context.go
@@ -179,6 +179,8 @@ func (x *jsonSource) Int64Slice(name string) ([]int64, error) {
 		for _, s := range v {
 			if i2, ok := s.(int64); ok {
 				c = append(c, i2)
+			} else if f2, ok := s.(float64); ok {
+				c = append(c, int64(f2))
 			} else {
 				return c, fmt.Errorf("unexpected item type %T in %T for %q", s, c, name)
 			}
@@ -206,6 +208,8 @@ func (x *jsonSource) Uint64Slice(name string) ([]uint64, error) {
 		for _, s := range v {
 			if i2, ok := s.(uint64); ok {
 				c = append(c, i2)
+			} else if f2, ok := s.(float64); ok {
+				c = append(c, uint64(f2))
 			} else {
 				return c, fmt.Errorf("unexpected item type %T in %T for %q", s, c, name)
 			}