lib/PublicInbox/ExtSearchIdx.pm | 3 ++-
 lib/PublicInbox/Import.pm       | 4 ++--
 lib/PublicInbox/LEI.pm          | 6 ++----
 lib/PublicInbox/Spawn.pm        | 5 ++---
 lib/PublicInbox/TestCommon.pm   | 9 +++++----
 t/spawn.t                       | 6 ++++++

diff --git a/lib/PublicInbox/ExtSearchIdx.pm b/lib/PublicInbox/ExtSearchIdx.pm
index a4b3bbd5e57c3255920e89e21b5e95e5a3d6116d..d0c9c2f7075d65034a3259d1024c9a0b77855e24 100644
--- a/lib/PublicInbox/ExtSearchIdx.pm
+++ b/lib/PublicInbox/ExtSearchIdx.pm
@@ -1011,8 +1011,9 @@ 	my ($self) = @_;
 	delete $self->{-commit_timer};
 	eidxq_process($self, $self->{-watch_sync});
 	eidxq_release($self);
-	delete local $self->{-watch_sync}->{-regen_fmt};
+	my $fmt = delete $self->{-watch_sync}->{-regen_fmt};
 	reindex_checkpoint($self, $self->{-watch_sync});
+	$self->{-watch_sync}->{-regen_fmt} = $fmt;
 
 	# call event_step => done unless commit_timer is armed
 	PublicInbox::DS::requeue($self);
diff --git a/lib/PublicInbox/Import.pm b/lib/PublicInbox/Import.pm
index e803ee74c2b8d06c11e7361ef0f32a5d5fd1363e..b8fa5c217ed99b344019e423cd4a384e6f5bd38c 100644
--- a/lib/PublicInbox/Import.pm
+++ b/lib/PublicInbox/Import.pm
@@ -21,8 +21,8 @@ use POSIX qw(strftime);
 
 sub default_branch () {
 	state $default_branch = do {
-		delete local $ENV{GIT_CONFIG};
-		my $r = popen_rd([qw(git config --global init.defaultBranch)]);
+		my $r = popen_rd([qw(git config --global init.defaultBranch)],
+				 { GIT_CONFIG => undef });
 		chomp(my $h = <$r> // '');
 		close $r;
 		$h eq '' ? 'refs/heads/master' : $h;
diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index fec00c020487daa696b911a144aa0f9a8fb17124..28e5365ad6b8bf75d302b8472941e50561446187 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -641,13 +641,11 @@ }
 
 sub _config {
 	my ($self, @argv) = @_;
-	my $env = $self->{env};
-	delete local $env->{GIT_CONFIG};
-	delete local $ENV{GIT_CONFIG};
+	my %env = (%{$self->{env}}, GIT_CONFIG => undef);
 	my $cfg = _lei_cfg($self, 1);
 	my $cmd = [ qw(git config -f), $cfg->{'-f'}, @argv ];
 	my %rdr = map { $_ => $self->{$_} } (0..2);
-	waitpid(spawn($cmd, $env, \%rdr), 0);
+	waitpid(spawn($cmd, \%env, \%rdr), 0);
 }
 
 sub lei_config {
diff --git a/lib/PublicInbox/Spawn.pm b/lib/PublicInbox/Spawn.pm
index 00e6829e9483918c92bccefef153c1477c084b2f..fe7aa0a8b5f6fce9a0326cced1efb2a41f84ce6b 100644
--- a/lib/PublicInbox/Spawn.pm
+++ b/lib/PublicInbox/Spawn.pm
@@ -358,10 +358,9 @@ 	my ($cmd, $env, $opts) = @_;
 	my $f = which($cmd->[0]) // die "$cmd->[0]: command not found\n";
 	my @env;
 	$opts ||= {};
-
-	my %env = $env ? (%ENV, %$env) : %ENV;
+	my %env = (%ENV, $env ? %$env : ());
 	while (my ($k, $v) = each %env) {
-		push @env, "$k=$v";
+		push @env, "$k=$v" if defined($v);
 	}
 	my $redir = [];
 	for my $child_fd (0..2) {
diff --git a/lib/PublicInbox/TestCommon.pm b/lib/PublicInbox/TestCommon.pm
index ca05fa215664c5cd6960f4ba0982afce6ba323c5..fc32b57fe92fc7d93ed79f2e38ecf58f0f093738 100644
--- a/lib/PublicInbox/TestCommon.pm
+++ b/lib/PublicInbox/TestCommon.pm
@@ -483,10 +483,11 @@ 	my $test_opt = shift // {};
 	require_git(2.6, 1) or skip('git 2.6+ required for lei test', 2);
 	require_mods(qw(json DBD::SQLite Search::Xapian), 2);
 	require PublicInbox::Config;
-	delete local $ENV{XDG_DATA_HOME};
-	delete local $ENV{XDG_CONFIG_HOME};
-	local $ENV{GIT_COMMITTER_EMAIL} = 'lei@example.com';
-	local $ENV{GIT_COMMITTER_NAME} = 'lei user';
+	local %ENV = %ENV;
+	delete $ENV{XDG_DATA_HOME};
+	delete $ENV{XDG_CONFIG_HOME};
+	$ENV{GIT_COMMITTER_EMAIL} = 'lei@example.com';
+	$ENV{GIT_COMMITTER_NAME} = 'lei user';
 	my (undef, $fn, $lineno) = caller(0);
 	my $t = "$fn:$lineno";
 	require PublicInbox::Spawn;
diff --git a/t/spawn.t b/t/spawn.t
index a17b72d97ff5926d41477647b0ffc273d16d5dc2..6168c1f6171c83919efefa91d7194a5a8b069c1b 100644
--- a/t/spawn.t
+++ b/t/spawn.t
@@ -121,6 +121,12 @@ 	ok(!close($fh), 'close fails on false');
 	isnt($?, 0, '$? set properly: '.$?);
 }
 
+{
+	local $ENV{GIT_CONFIG} = '/path/to/this/better/not/exist';
+	my $fh = popen_rd([qw(env)], { GIT_CONFIG => undef });
+	ok(!grep(/^GIT_CONFIG=/, <$fh>), 'GIT_CONFIG clobbered');
+}
+
 { # ->CLOSE vs ->DESTROY waitpid caller distinction
 	my @c;
 	my $fh = popen_rd(['true'], undef, { cb => sub { @c = caller } });