diff --git a/README.md b/README.md
index ce121f8..bf62f1e 100644
--- a/README.md
+++ b/README.md
@@ -138,7 +138,7 @@ some additional placeholders. The complete list is:
            INSERT clause
 ?ident     used for identifiers (column or table name)
 ?ident...  expands identifiers and separates them with a comma
-?sql       inserts the parameter as is (meant for SQL parts)
+?sql       inserts the parameter, a string or Marshaler, as is (meant for SQL parts)
 ```
 
 Using the placeholders it is easy and quite expressive to write common SQL queries, but it is
diff --git a/doc.go b/doc.go
index 09b1f98..32cd586 100644
--- a/doc.go
+++ b/doc.go
@@ -23,7 +23,7 @@
 //              INSERT clause
 //   ?ident     used for identifiers (column or table name)
 //   ?ident...  expands identifiers and separates them with a comma
-//   ?sql       inserts the parameter as is (meant for SQL parts)
+//   ?sql       inserts the parameter, a string or Marshaler, as is (meant for SQL parts)
 //
 // Prepared statements
 //