diff --git a/NEWS.md b/NEWS.md
index dfc443861..ce2ba24be 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -130,6 +130,7 @@
 
 6. New vignette _Using `.SD` for Data Analysis_, a deep dive into use cases for the `.SD` variable to help illuminate this topic which we've found to be a sticking point for beginning and intermediate `data.table` users, [#3412](https://github.com/Rdatatable/data.table/issues/3412).
 
+7. Added a note to `?frank` clarifying that ranking is being done according to C sorting (i.e., like `forder`), [#2328](https://github.com/Rdatatable/data.table/issues/2328). Thanks to @cguill95 for the request.
 
 ### Changes in [v1.12.2](https://github.com/Rdatatable/data.table/milestone/14?closed=1)  (07 Apr 2019)
 
diff --git a/man/frank.Rd b/man/frank.Rd
index 89aad0df6..93d5a6d73 100644
--- a/man/frank.Rd
+++ b/man/frank.Rd
@@ -5,6 +5,8 @@
 \title{Fast rank}
 \description{
   Similar to \code{base::rank} but \emph{much faster}. And it accepts vectors, lists, data.frames or data.tables as input. In addition to the \code{ties.method} possibilities provided by \code{base::rank}, it also provides \code{ties.method="dense"}.
+  
+  Like \code{\link{forder}}, sorting is done in "C-locale"; in particular, this may affect how capital/lowercase letters are ranked. See Details on \code{forder} for more.
 
   \code{bit64::integer64} type is also supported.
 }