diff --git a/doc/mlr.1 b/doc/mlr.1
index 0ddc597b32..a9c79fe9a6 100644
--- a/doc/mlr.1
+++ b/doc/mlr.1
@@ -469,7 +469,7 @@ Options:
 -F: Keeps field values, or literals in the expression, as strings or floats
     with no inference to int.
 -x: Prints records for which {expression} evaluates to false.
--f {expression}: the DSL expression is taken from the specified file rather
+-f {filename}: the DSL expression is taken from the specified file rather
     than from the command line.
 
 Please use a dollar sign for field names and double-quotes for string
@@ -770,7 +770,7 @@ Options:
     with no inference to int.
 --oflatsep {string}: Separator to use when flattening multi-level @-variables
     to output records for emit. Default ":".
--f {expression}: the DSL expression is taken from the specified file rather
+-f {filename}: the DSL expression is taken from the specified file rather
     than from the command line.
 
 Please use a dollar sign for field names and double-quotes for string
diff --git a/doc/reference.html b/doc/reference.html
index 3a31dd1750..74359f06b2 100644
--- a/doc/reference.html
+++ b/doc/reference.html
@@ -1292,7 +1292,7 @@
 -F: Keeps field values, or literals in the expression, as strings or floats
     with no inference to int.
 -x: Prints records for which {expression} evaluates to false.
--f {expression}: the DSL expression is taken from the specified file rather
+-f {filename}: the DSL expression is taken from the specified file rather
     than from the command line.
 
 Please use a dollar sign for field names and double-quotes for string
@@ -2176,7 +2176,7 @@
     with no inference to int.
 --oflatsep {string}: Separator to use when flattening multi-level @-variables
     to output records for emit. Default ":".
--f {expression}: the DSL expression is taken from the specified file rather
+-f {filename}: the DSL expression is taken from the specified file rather
     than from the command line.
 
 Please use a dollar sign for field names and double-quotes for string