diff -urNp -x '*.orig' openldap-2.4.49.org/servers/slapd/back-perl/init.c openldap-2.4.49/servers/slapd/back-perl/init.c
--- openldap-2.4.49.org/servers/slapd/back-perl/init.c	2020-01-30 18:58:35.000000000 +0100
+++ openldap-2.4.49/servers/slapd/back-perl/init.c	2021-05-07 23:04:45.762194508 +0200
@@ -23,7 +23,7 @@
 extern char **environ;
 #endif
 
-static void perl_back_xs_init LDAP_P((PERL_BACK_XS_INIT_PARAMS));
+XSINIT_t perl_back_xs_init LDAP_P((PERL_BACK_XS_INIT_PARAMS));
 EXT void boot_DynaLoader LDAP_P((PERL_BACK_BOOT_DYNALOADER_PARAMS));
 
 PerlInterpreter *PERL_INTERPRETER = NULL;
@@ -159,7 +159,7 @@ perl_back_db_open(
 }
 
 
-static void
+XSINIT_t
 perl_back_xs_init(PERL_BACK_XS_INIT_PARAMS)
 {
 	char *file = __FILE__;
diff -urNp -x '*.orig' openldap-2.4.49.org/servers/slapd/back-perl/perl_back.h openldap-2.4.49/servers/slapd/back-perl/perl_back.h
--- openldap-2.4.49.org/servers/slapd/back-perl/perl_back.h	2020-01-30 18:58:35.000000000 +0100
+++ openldap-2.4.49/servers/slapd/back-perl/perl_back.h	2021-05-07 23:04:45.762194508 +0200
@@ -36,6 +36,9 @@ LDAP_BEGIN_DECL
 #if defined(pTHX_) || (PERL_REVISION > 5 || (PERL_REVISION == 5 && PERL_VERSION >= 6))
 #define PERL_IS_5_6
 #endif
+#if ( PERL_REVISION > 5 || (PERL_REVISION == 5 && PERL_VERSION >= 8 ))
+#define PERL_IS_5_8
+#endif
 
 #define EVAL_BUF_SIZE 500
 
@@ -52,7 +55,7 @@ extern ldap_pvt_thread_mutex_t  perl_int
 # define ERRSV	GvSV(errgv)
 #endif
 
-#if defined( HAVE_WIN32_ASPERL ) || defined( USE_ITHREADS )
+#if defined( HAVE_WIN32_ASPERL ) || defined( USE_ITHREADS ) || defined( PERL_IS_5_8 )
 /* pTHX is needed often now */
 # define PERL_INTERPRETER			my_perl
 # define PERL_BACK_XS_INIT_PARAMS		pTHX