diff --git a/exec.go b/exec.go
index d73518f6c..01c4db8d7 100644
--- a/exec.go
+++ b/exec.go
@@ -50,9 +50,9 @@ following will output a list of processes running in the container:
 			Name:  "user, u",
 			Usage: "UID (format: <uid>[:<gid>])",
 		},
-		cli.StringFlag{
+		cli.Int64SliceFlag{
 			Name:  "additional-gids, g",
-			Usage: "additional gids separated by comma",
+			Usage: "additional gids",
 		},
 		cli.StringFlag{
 			Name:  "process, p",
@@ -212,14 +212,8 @@ func getProcess(context *cli.Context, bundle string) (*specs.Process, error) {
 		}
 		p.User.UID = uint32(uid)
 	}
-	if context.String("additional-gids") != "" {
-		for _, i := range strings.Split(context.String("additional-gids"), ",") {
-			gid, err := strconv.Atoi(i)
-			if err != nil {
-				return nil, fmt.Errorf("parsing %s as int for gid failed: %v", i, err)
-			}
-			p.User.AdditionalGids = append(p.User.AdditionalGids, uint32(gid))
-		}
+	for _, gid := range context.Int64Slice("additional-gids") {
+		p.User.AdditionalGids = append(p.User.AdditionalGids, uint32(gid))
 	}
 	return p, nil
 }
diff --git a/man/runc-exec.8.md b/man/runc-exec.8.md
index 46b266175..318d4a430 100644
--- a/man/runc-exec.8.md
+++ b/man/runc-exec.8.md
@@ -19,7 +19,7 @@ following will output a list of processes running in the container:
    --env value, -e value                    set environment variables
    --tty, -t                                allocate a pseudo-TTY
    --user value, -u value                   UID (format: <uid>[:<gid>])
-   --additional-gids value, -g value        additional gids separated by comma
+   --additional-gids value, -g value        additional gids
    --process value, -p value                path to the process.json
    --detach, -d                             detach from the container's process
    --pid-file value                         specify the file to write the process id to
diff --git a/tests/integration/exec.bats b/tests/integration/exec.bats
index c7774a0eb..b1f86a386 100644
--- a/tests/integration/exec.bats
+++ b/tests/integration/exec.bats
@@ -120,8 +120,8 @@ function teardown() {
 
   wait_for_container 15 1 test_busybox
 
-  runc exec --user 1000:1000 --additional-gids 100 test_busybox id
+  runc exec --user 1000:1000 --additional-gids 100 --additional-gids 99 test_busybox id 
   [ "$status" -eq 0 ]
 
-  [[ ${output} == "uid=1000 gid=1000 groups=100(users)" ]]
+  [[ ${output} == "uid=1000 gid=1000 groups=99(nogroup),100(users)" ]]
 }