diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 92231c66da..262760f8c0 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -816,7 +816,7 @@ __git_aliases ()
 __git_aliased_command ()
 {
 	local word cmdline=$(git --git-dir="$(__gitdir)" \
-		config --get "alias.$1")
+		config --get "alias.$1" 2>/dev/null)
 	for word in $cmdline; do
 		case "$word" in
 		\!gitk|gitk)
@@ -2800,7 +2800,7 @@ __git_main ()
 		--git-dir)   ((c++)) ; __git_dir="${words[c]}" ;;
 		--bare)      __git_dir="." ;;
 		--help) command="help"; break ;;
-		-c|--work-tree|--namespace) ((c++)) ;;
+		-c|-C|--work-tree|--namespace) ((c++)) ;;
 		-*) ;;
 		*) command="$i"; break ;;
 		esac
@@ -2844,13 +2844,13 @@ __git_main ()
 	fi
 
 	local completion_func="_git_${command//-/_}"
-	declare -f $completion_func >/dev/null && $completion_func && return
+	declare -f $completion_func >/dev/null 2>/dev/null && $completion_func && return
 
 	local expansion=$(__git_aliased_command "$command")
 	if [ -n "$expansion" ]; then
 		words[1]=$expansion
 		completion_func="_git_${expansion//-/_}"
-		declare -f $completion_func >/dev/null && $completion_func
+		declare -f $completion_func >/dev/null 2>/dev/null && $completion_func
 	fi
 }
 
diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index 500505dca1..be2ed87043 100755
--- a/t/t9902-completion.sh
+++ b/t/t9902-completion.sh
@@ -755,7 +755,12 @@ test_expect_success 'general options plus command' '
 	test_completion "git --namespace=foo check" "checkout " &&
 	test_completion "git --paginate check" "checkout " &&
 	test_completion "git --info-path check" "checkout " &&
-	test_completion "git --no-replace-objects check" "checkout "
+	test_completion "git --no-replace-objects check" "checkout " &&
+	test_completion "git --git-dir some/path check" "checkout " &&
+	test_completion "git -c conf.var=value check" "checkout " &&
+	test_completion "git -C some/path check" "checkout " &&
+	test_completion "git --work-tree some/path check" "checkout " &&
+	test_completion "git --namespace name/space check" "checkout "
 '
 
 test_expect_success 'git --help completion' '