1 files changed, 7 insertions, 2 deletions
diff --git a/mg.c b/mg.c
index 340ab6a425..51a12f1c6c 100644
--- a/mg.c
+++ b/mg.c
@@ -1780,16 +1780,21 @@ Perl_magic_setsubstr(pTHX_ SV *sv, MAGIC *mg)
 	sv_utf8_upgrade(lsv);
  	sv_pos_u2b(lsv, &lvoff, &lvlen);
 	sv_insert(lsv, lvoff, lvlen, tmps, len);
+	LvTARGLEN(sv) = sv_len_utf8(sv);
 	SvUTF8_on(lsv);
     }
     else if (lsv && SvUTF8(lsv)) {
 	sv_pos_u2b(lsv, &lvoff, &lvlen);
+	LvTARGLEN(sv) = len;
 	tmps = (char*)bytes_to_utf8((U8*)tmps, &len);
 	sv_insert(lsv, lvoff, lvlen, tmps, len);
 	Safefree(tmps);
     }
-    else
-        sv_insert(lsv, lvoff, lvlen, tmps, len);
+    else {
+	sv_insert(lsv, lvoff, lvlen, tmps, len);
+	LvTARGLEN(sv) = len;
+    }
+
 
     return 0;
 }