diff --git a/R/data.table.R b/R/data.table.R
index 0dd0b7f5f..1c2c07a3f 100644
--- a/R/data.table.R
+++ b/R/data.table.R
@@ -123,6 +123,7 @@ replace_dot_alias = function(e) {
       stopf("Object '%s' not found amongst %s", used, brackify(ref))
     }
   } else {
+    # Don't use stopf() directly, since err$message might have '%', #6588
     stopf("%s", err$message, domain=NA)
   }
 }