Index: src/pmc/fixedpmcarray.pmc
===================================================================
--- src/pmc/fixedpmcarray.pmc	(revision 42529)
+++ src/pmc/fixedpmcarray.pmc	(working copy)
@@ -484,9 +484,10 @@
         else {
             PMC *box = SELF.get_pmc_keyed_int(k);
 
-            /* RT #46675: autovivify an Array and insert it in SELF */
-            if (!box)
+            if (!box) {
                 box = pmc_new(INTERP, SELF.type());
+                SELF.set_pmc_keyed_int(k, box);
+            }
 
             VTABLE_set_number_keyed(INTERP, box, nextkey, value);
         }
@@ -572,9 +573,10 @@
         else {
             PMC *box = SELF.get_pmc_keyed_int(k);
 
-            /* RT #46675: autovivify an Array and insert it in SELF */
-            if (!box)
+            if (!box) {
                 box = pmc_new(INTERP, SELF.type());
+                VTABLE_set_pmc_keyed_int(INTERP, SELF, k, box);
+            }
 
             VTABLE_set_pmc_keyed(INTERP, box, nextkey, value);
         }