1 files changed, 2 insertions, 0 deletions
diff --git a/pp.c b/pp.c
index 5b09c082d1..3551d8f1ea 100644
--- a/pp.c
+++ b/pp.c
@@ -3178,6 +3178,8 @@ PP(pp_substr)
 		repl = SvPV_const(repl_sv_copy, repl_len);
 		repl_is_utf8 = DO_UTF8(repl_sv_copy) && SvCUR(sv);
 	    }
+	    if (!SvOK(sv))
+		sv_setpvs(sv, "");
 	    sv_insert(sv, pos, rem, repl, repl_len);
 	    if (repl_is_utf8)
 		SvUTF8_on(sv);