1 files changed, 3 insertions, 0 deletions
diff --git a/string.c b/string.c
index 692a158c09..b2761f04eb 100644
--- a/string.c
+++ b/string.c
@@ -1063,6 +1063,9 @@ rb_str_match2(str)
     VALUE str;
 {
     StringValue(str);
+#if RUBY_VERSION_CODE < 181
+	rb_warn("~string will be obsolete; use explicit regexp");
+#endif
     return rb_reg_match2(rb_reg_regcomp(rb_reg_quote(str)));
 }