diff --git a/src/if_perl.xs b/src/if_perl.xs

index c69ed9ef1..2cf78b901 100644

--- a/src/if_perl.xs

+++ b/src/if_perl.xs

@@ -40,7 +40,7 @@

 /* Work around for perl-5.18.

  * Don't include "perl\lib\CORE\inline.h" for now,

  * include it after Perl_sv_free2 is defined. */

-#ifdef DYNAMIC_PERL

+#if (PERL_REVISION == 5) && (PERL_VERSION >= 18)

 # define PERL_NO_INLINE_FUNCTIONS

 #endif

@@ -402,14 +402,14 @@ static bool (*Perl_sv_2bool)(pTHX_ SV*);

 static IV (*Perl_sv_2iv)(pTHX_ SV*);

 static SV* (*Perl_sv_2mortal)(pTHX_ SV*);

 # if (PERL_REVISION == 5) && (PERL_VERSION >= 8)

-static char* (*Perl_sv_2pv_flags)(pTHX_ SV*, STRLEN*, I32);

+static char* (*Perl_sv_2pv_flags)(pTHX_ SV*, STRLEN* const, const U32);

 static char* (*Perl_sv_2pv_nolen)(pTHX_ SV*);

 # else

 static char* (*Perl_sv_2pv)(pTHX_ SV*, STRLEN*);

 # endif

 static char* (*Perl_sv_2pvbyte)(pTHX_ SV*, STRLEN*);

 # if (PERL_REVISION == 5) && (PERL_VERSION >= 32)

-static char* (*Perl_sv_2pvbyte_flags)(pTHX_ SV*, STRLEN*, I32);

+static char* (*Perl_sv_2pvbyte_flags)(pTHX_ SV*, STRLEN* const, const U32);

 # endif

 static SV* (*Perl_sv_bless)(pTHX_ SV*, HV*);

 # if (PERL_REVISION == 5) && (PERL_VERSION >= 8)

@@ -710,7 +710,7 @@ S_POPMARK(pTHX)

 # endif

 /* perl-5.34 needs Perl_SvTRUE_common; used in SvTRUE_nomg_NN */

-# if (PERL_REVISION == 5) && (PERL_VERSION >= 34)

+# if (PERL_REVISION == 5) && (PERL_VERSION == 34)

 PERL_STATIC_INLINE bool

 Perl_SvTRUE_common(pTHX_ SV * sv, const bool sv_2bool_is_fallback)

 {

@@ -737,7 +737,7 @@ Perl_SvTRUE_common(pTHX_ SV * sv, const bool sv_2bool_is_fallback)

 # endif

 /* perl-5.32 needs Perl_SvTRUE */

-# if (PERL_REVISION == 5) && (PERL_VERSION >= 32)

+# if (PERL_REVISION == 5) && (PERL_VERSION == 32)

 PERL_STATIC_INLINE bool

 Perl_SvTRUE(pTHX_ SV *sv) {

     if (!LIKELY(sv))