diff --git a/README.rst b/README.rst
index c3c8987..bc27ab7 100644
--- a/README.rst
+++ b/README.rst
@@ -68,6 +68,7 @@ Usage
 
     usage: pigar [-h] [-v] [-u] [-s NAME [NAME ...]] [-c [PATH]] [-l LOG_LEVEL]
                  [-i DIR [DIR ...]] [-p SAVE_PATH] [-P PROJECT_PATH]
+                 [-o COMPARISON_OPERATOR]
 
     Python requirements tool -- pigar, it will do only one thing at each time.
     Default action is generate requirements.txt in current directory.
@@ -92,6 +93,9 @@ Usage
                           action
       -P PROJECT_PATH     project path, which is directory, *used for* default
                           action
+      -o COMPARISON_OPERATOR
+                          The comparison operator for versions, alternatives:
+                          [==, ~=, >=]
 
 
 More
diff --git a/pigar/_version.py b/pigar/_version.py
index 86e0dad..5c9a785 100644
--- a/pigar/_version.py
+++ b/pigar/_version.py
@@ -2,5 +2,5 @@
 
 from __future__ import print_function, division, absolute_import
 
-version = __version__ = '0.9.1'
+version = __version__ = '0.9.2'
 version_info = [int(num) for num in version.split('.')]
diff --git a/pigar/cmd.py b/pigar/cmd.py
index dde58db..935e09f 100644
--- a/pigar/cmd.py
+++ b/pigar/cmd.py
@@ -77,7 +77,7 @@ def parse_args(args=None):
         default=[os.getcwd()],
         help='project path, which is directory, *used for* default action')
     parser.add_argument(
-        '-o', '--comparison-operator',
+        '-o',  # '--comparison-operator',
         dest='comparison_operator',
         nargs=1,
         type=comparison_operator_check,