diff --git a/dvc/command/diff.py b/dvc/command/diff.py
index 8cb5d5c237..36e9e51980 100644
--- a/dvc/command/diff.py
+++ b/dvc/command/diff.py
@@ -142,7 +142,7 @@ def add_parser(subparsers, parent_parser):
     )
     diff_parser.add_argument(
         "--checksums",
-        help=("Display checksums of each entry"),
+        help=("Display checksums for each entry"),
         action="store_true",
         default=False,
     )
diff --git a/scripts/completion/dvc.bash b/scripts/completion/dvc.bash
index 2af965a67d..128a64326f 100644
--- a/scripts/completion/dvc.bash
+++ b/scripts/completion/dvc.bash
@@ -22,7 +22,7 @@ _dvc_checkout='-d --with-deps -R --recursive -f --force --relink $(compgen -G *.
 _dvc_commit='-f --force -d --with-deps -R --recursive $(compgen -G *.dvc)'
 _dvc_config='-u --unset --local --system --global'
 _dvc_destroy='-f --force'
-_dvc_diff='-t --target'
+_dvc_diff='-t --target --json --checksums'
 _dvc_fetch='-j --jobs -r --remote -a --all-branches -T --all-tags -d --with-deps -R --recursive $(compgen -G *.dvc)'
 _dvc_get_url=''
 _dvc_get='-o --out --rev --show-url'
diff --git a/scripts/completion/dvc.zsh b/scripts/completion/dvc.zsh
index 32bdef47ff..be47469d5e 100644
--- a/scripts/completion/dvc.zsh
+++ b/scripts/completion/dvc.zsh
@@ -98,6 +98,9 @@ _dvc_destroy=(
 
 _dvc_diff=(
   {-t,--target}"[Source path to a data file or directory.]:Target files:"
+  "--json[Format the output into a JSON]"
+  "--checksums[Display checksums for each entry]"
+  {1,2}":Git revision (e.g. branch, tag, SHA):"
 )
 
 _dvc_fetch=(