diff --git a/builtin/grep.c b/builtin/grep.c
index 3ca4ac80d8c7014e7e9aba228f542113a5103b48..496f33336ef7d882bef1ea2da87c276db78a2160 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -832,8 +832,9 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 		OPT_BOOL('L', "files-without-match",
 			&opt.unmatch_name_only,
 			N_("show only the names of files without match")),
-		OPT_BOOL('z', "null", &opt.null_following_name,
-			N_("print NUL after filenames")),
+		OPT_BOOL_F('z', "null", &opt.null_following_name,
+			   N_("print NUL after filenames"),
+			   PARSE_OPT_NOCOMPLETE),
 		OPT_BOOL('c', "count", &opt.count,
 			N_("show the number of matches instead of matching lines")),
 		OPT__COLOR(&opt.color, N_("highlight matches")),
@@ -884,9 +885,11 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 		OPT_GROUP(""),
 		{ OPTION_STRING, 'O', "open-files-in-pager", &show_in_pager,
 			N_("pager"), N_("show matching files in the pager"),
-			PARSE_OPT_OPTARG, NULL, (intptr_t)default_pager },
-		OPT_BOOL(0, "ext-grep", &external_grep_allowed__ignored,
-			 N_("allow calling of grep(1) (ignored by this build)")),
+			PARSE_OPT_OPTARG | PARSE_OPT_NOCOMPLETE,
+			NULL, (intptr_t)default_pager },
+		OPT_BOOL_F(0, "ext-grep", &external_grep_allowed__ignored,
+			   N_("allow calling of grep(1) (ignored by this build)"),
+			   PARSE_OPT_NOCOMPLETE),
 		OPT_END()
 	};
 
diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 79e9f69d52e89c534d27df517f0007760bc651d9..60d27253ee895f2704182889004ad2772fa65776 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -1565,21 +1565,7 @@ _git_grep ()
 
 	case "$cur" in
 	--*)
-		__gitcomp "
-			--cached
-			--text --ignore-case --word-regexp --invert-match
-			--full-name --line-number
-			--extended-regexp --basic-regexp --fixed-strings
-			--perl-regexp
-			--threads
-			--files-with-matches --name-only
-			--files-without-match
-			--max-depth
-			--count
-			--and --or --not --all-match
-			--break --heading --show-function --function-context
-			--untracked --no-index
-			"
+		__gitcomp_builtin grep
 		return
 		;;
 	esac