1 files changed, 15 insertions, 1 deletions
diff --git a/mro.c b/mro.c
index a7ea282dc0..ffb72abfc5 100644
--- a/mro.c
+++ b/mro.c
@@ -193,9 +193,23 @@ S_mro_get_linear_isa_dfs(pTHX_ HV *stash, I32 level)
 		    /* It was newly created.  Steal it for our new SV, and
 		       replace it in the hash with the "real" thing.  */
 		    SV *const val = HeVAL(he);
+		    HEK *const key = HeKEY_hek(he);
 
 		    HeVAL(he) = &PL_sv_undef;
-		    sv_setsv(val, subsv);
+		    /* Save copying by making a shared hash key scalar. We
+		       inline this here rather than calling Perl_newSVpvn_share
+		       because we already have the scalar, and we already have
+		       the hash key.  */
+		    assert(SvTYPE(val) == SVt_NULL);
+		    sv_upgrade(val, SVt_PV);
+		    SvPV_set(val, HEK_KEY(share_hek_hek(key)));
+		    SvCUR_set(val, HEK_LEN(key));
+		    SvREADONLY_on(val);
+		    SvFAKE_on(val);
+		    SvPOK_on(val);
+		    if (HEK_UTF8(key))
+			SvUTF8_on(val);
+
 		    av_push(retval, val);
 		}
             }