diff --git a/miniserv.pl b/miniserv.pl
index 2133f9f3e..21b32b84d 100755
--- a/miniserv.pl
+++ b/miniserv.pl
@@ -143,9 +143,18 @@ if (-l $perl_path) {
 if (open(PIDFILE, $config{'pidfile'})) {
 	my $already = <PIDFILE>;
 	close(PIDFILE);
-	chop($already);
-	if ($already && $already != $$ && kill(0, $already)) {
-		die "Webmin is already running with PID $already\n";
+	chomp($already);
+	$already =~ s/^\s+|\s+$//g;
+	if ($already =~ /^\d+$/ && $already != $$ && kill(0, $already)) {
+		my $active = &pid_is_miniserv_for_config($already, $config_file);
+		if (defined($active) && !$active) {
+			warn "Ignoring stale Webmin PID file $config{'pidfile'} ".
+			     "for unrelated PID $already\n";
+			unlink($config{'pidfile'});
+			}
+		else {
+			die "Webmin is already running with PID $already\n";
+			}
 		}
 	}
 
@@ -5182,6 +5191,56 @@ close($fh);
 return $rv;
 }
 
+# read_process_cmdline(pid)
+# Returns a process command line from /proc, or undef if unavailable.
+sub read_process_cmdline
+{
+my ($pid) = @_;
+return undef if (!$pid || $pid !~ /^\d+$/);
+return &read_any_file("/proc/$pid/cmdline");
+}
+
+# same_config_file(file1, file2)
+# Returns 1 if two config paths refer to the same file.
+sub same_config_file
+{
+my ($file1, $file2) = @_;
+return 0 if (!$file1 || !$file2);
+return 1 if ($file1 eq $file2);
+my @stat1 = stat($file1);
+my @stat2 = stat($file2);
+return @stat1 && @stat2 && $stat1[0] == $stat2[0] &&
+       $stat1[1] == $stat2[1];
+}
+
+# pid_is_miniserv_for_config(pid, config-file)
+# Returns 1 if pid appears to be miniserv for this config, 0 if it is a
+# different process, or undef if this platform cannot tell.
+sub pid_is_miniserv_for_config
+{
+my ($pid, $config_file) = @_;
+my $cmdline = &read_process_cmdline($pid);
+return undef if (!defined($cmdline));
+return 0 if ($cmdline eq "");
+my @args = split(/\0/, $cmdline);
+my $script_idx;
+for(my $i=0; $i<@args; $i++) {
+	if ($args[$i] =~ /(?:^|\/)miniserv\.pl$/) {
+		$script_idx = $i;
+		last;
+		}
+	}
+return 0 if (!defined($script_idx));
+my $config_arg;
+for(my $i=$script_idx+1; $i<@args; $i++) {
+	next if ($args[$i] =~ /^-/);
+	$config_arg = $args[$i];
+	last;
+	}
+return defined($config_arg) ?
+       (&same_config_file($config_arg, $config_file) ? 1 : 0) : undef;
+}
+
 # update_vital_config()
 # Updates %config with defaults, and dies if something vital is missing
 sub update_vital_config
diff --git a/t/miniserv.t b/t/miniserv.t
index 59a690352..05c4fcd97 100644
--- a/t/miniserv.t
+++ b/t/miniserv.t
@@ -1282,6 +1282,70 @@ subtest 'read_any_file' => sub {
 	   'open failure returns undef');
 };
 
+# pid_is_miniserv_for_config — avoids stale pidfiles with reused PIDs
+subtest 'pid_is_miniserv_for_config' => sub {
+	my $config = '/etc/webmin/miniserv.conf';
+	my $pid = $$;
+
+	{
+		no warnings 'redefine';
+		local *miniserv::read_process_cmdline = sub {
+			return join("\0", '/usr/sbin/dovecot', '-F');
+			};
+		is(miniserv::pid_is_miniserv_for_config($pid, $config), 0,
+		   'live unrelated PID is not treated as active miniserv');
+	}
+
+	{
+		no warnings 'redefine';
+		local *miniserv::read_process_cmdline = sub {
+			return join("\0", '/usr/bin/perl',
+				    '/usr/libexec/webmin/miniserv.pl',
+				    '--nofork', $config);
+			};
+		is(miniserv::pid_is_miniserv_for_config($pid, $config), 1,
+		   'matching miniserv config is treated as active');
+	}
+
+	{
+		require File::Temp;
+		my ($fh, $real_config) = File::Temp::tempfile(UNLINK => 1);
+		close($fh);
+		my $link_config = "$real_config.link";
+		SKIP: {
+			symlink($real_config, $link_config) ||
+				skip 'symlinks are unavailable', 1;
+			no warnings 'redefine';
+			local *miniserv::read_process_cmdline = sub {
+				return join("\0", '/usr/bin/perl',
+					    '/usr/libexec/webmin/miniserv.pl',
+					    $link_config);
+				};
+			is(miniserv::pid_is_miniserv_for_config($pid, $real_config), 1,
+			   'symlinked config path is matched by inode');
+			unlink($link_config);
+			}
+	}
+
+	{
+		no warnings 'redefine';
+		local *miniserv::read_process_cmdline = sub {
+			return join("\0", '/usr/bin/perl',
+				    '/usr/libexec/usermin/miniserv.pl',
+				    '--nofork', '/etc/usermin/miniserv.conf');
+			};
+		is(miniserv::pid_is_miniserv_for_config($pid, $config), 0,
+		   'different miniserv config is not treated as active');
+	}
+
+	{
+		no warnings 'redefine';
+		local *miniserv::read_process_cmdline = sub { return undef; };
+		is(miniserv::pid_is_miniserv_for_config($pid, $config), undef,
+		   'unreadable process command line keeps conservative behavior');
+	}
+};
+
 # read_mime_types — populates %mime from file + addtype_* config
 subtest 'read_mime_types' => sub {
 	no warnings 'once';