1 files changed, 9 insertions, 1 deletions
diff --git a/inline.h b/inline.h
index 72fe1d3cd4..d4794aa81a 100644
--- a/inline.h
+++ b/inline.h
@@ -3475,7 +3475,15 @@ Perl_mortal_getenv(const char * str)
 PERL_STATIC_INLINE bool
 Perl_sv_isbool(pTHX_ const SV *sv)
 {
-    return SvBoolFlagsOK(sv) && BOOL_INTERNALS_sv_isbool(sv);
+    /* change to the following in 5.37, logically the same but
+     * more efficient and more future proof */
+#if 0
+    return (SvBoolFlagsOK(sv) && BOOL_INTERNALS_sv_isbool(sv));
+#else
+    return SvIOK(sv) && SvPOK(sv) && SvIsCOW_static(sv) &&
+        (SvPVX_const(sv) == PL_Yes || SvPVX_const(sv) == PL_No);
+#endif
+
 }
 
 #ifdef USE_ITHREADS