-STATIC int vmg_svt_copy(pTHX_ SV *sv, MAGIC *mg, SV *nsv, const char *key, int keylen) {
+STATIC int vmg_svt_copy(pTHX_ SV *sv, MAGIC *mg, SV *nsv, const char *key,
+# if PERL_API_VERSION_GE(5, 11, 0)
+ I32 keylen
+# else
+ int keylen
+# endif
+ ) {