diff --git a/ext/re2/re2.cc b/ext/re2/re2.cc
index 89bcba5..4b23de4 100644
--- a/ext/re2/re2.cc
+++ b/ext/re2/re2.cc
@@ -1589,6 +1589,12 @@ static VALUE re2_set_add(VALUE self, VALUE pattern) {
 
   int index = s->set->Add(regex, &err);
   if (index < 0) {
+    char msg[100];
+    snprintf(msg, sizeof(msg), "str rejected by RE2::Set->Add(): %s",
+        err.c_str());
+
+    /* Manually destruct the error string before we throw an exception. */
+    err.~basic_string();
     rb_raise(rb_eArgError, "str rejected by RE2::Set->Add(): %s", err.c_str());
   }