diff --git a/ext/B/B.xs b/ext/B/B.xs
index e6e3fb830968..e89118502679 100644
--- a/ext/B/B.xs
+++ b/ext/B/B.xs
@@ -10,6 +10,7 @@
 #define PERL_NO_GET_CONTEXT
 #define PERL_EXT
 #include "EXTERN.h"
+#define PERL_IN_B_XS
 #include "perl.h"
 #include "XSUB.h"
 
diff --git a/invlist_inline.h b/invlist_inline.h
index f6ac81953355..1aec16a89a8a 100644
--- a/invlist_inline.h
+++ b/invlist_inline.h
@@ -15,7 +15,8 @@
  || defined(PERL_IN_TOKE_C)             \
  || defined(PERL_IN_PP_C)               \
  || defined(PERL_IN_OP_C)               \
- || defined(PERL_IN_DOOP_C)
+ || defined(PERL_IN_DOOP_C)             \
+ || defined(PERL_IN_B_XS)
 
 /* An element is in an inversion list iff its index is even numbered: 0, 2, 4,
  * etc */
diff --git a/op.c b/op.c
index 421387ed107b..8ea2e053653e 100644
--- a/op.c
+++ b/op.c
@@ -7909,6 +7909,7 @@ S_pmtrans(pTHX_ OP *o, OP *expr, OP *repl)
                       || r_map[len-1] == TR_SPECIAL_HANDLING))))
     {
         SV* r_map_sv;
+        SV* temp_sv;
 
         /* A UTF-8 op is generated, indicated by this flag.  This op is an
          * sv_op */
@@ -7920,19 +7921,26 @@ S_pmtrans(pTHX_ OP *o, OP *expr, OP *repl)
 
         /* The inversion map is pushed; first the list. */
 	invmap = MUTABLE_AV(newAV());
+
+        SvREADONLY_on(t_invlist);
         av_push(invmap, t_invlist);
 
         /* 2nd is the mapping */
         r_map_sv = newSVpvn((char *) r_map, len * sizeof(UV));
+        SvREADONLY_on(r_map_sv);
         av_push(invmap, r_map_sv);
 
         /* 3rd is the max possible expansion factor */
-        av_push(invmap, newSVnv(max_expansion));
+        temp_sv = newSVnv(max_expansion);
+        SvREADONLY_on(temp_sv);
+        av_push(invmap, temp_sv);
 
         /* Characters that are in the search list, but not in the replacement
          * list are mapped to the final character in the replacement list */
         if (! del && r_count < t_count) {
-            av_push(invmap, newSVuv(final_map));
+            temp_sv = newSVuv(final_map);
+            SvREADONLY_on(temp_sv);
+            av_push(invmap, temp_sv);
         }
 
 #ifdef USE_ITHREADS