diff --git a/README.md b/README.md
index b93769a..42bebb3 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,7 @@ pedump    [![Build Status](https://travis-ci.org/zed-0xff/pedump.png?branch=mast
 News
 ----
 ```
+2024.01.15 - add "--set-os-version VER" cmdline option for patching OS version in PE header
 2023.12.04 - workaround IO.pread() not available on windows
 2021.02.18 - updated gems; changed open-uri to URI.open; enabled SSL on https://pedump.me/
 2020.08.09 - CLI: added resource extracting with --extract ID
@@ -89,6 +90,7 @@ Usage
                                          ID: section:rva/0x1000 - section by RVA
                                          ID: section:raw/0x400  - section by RAW_PTR
             --va2file VA                 Convert RVA to file offset
+            --set-os-version VER         Patch OS version in PE header
     
         -W, --web                        Uploads files to a https://pedump.me
                                          for a nice HTML tables with image previews,
diff --git a/README.md.tpl b/README.md.tpl
index 6a540f7..b274b21 100644
--- a/README.md.tpl
+++ b/README.md.tpl
@@ -4,6 +4,8 @@ pedump    [![Build Status](https://travis-ci.org/zed-0xff/pedump.png?branch=mast
 News
 ----
 ```
+2024.01.15 - add "--set-os-version VER" cmdline option for patching OS version in PE header
+2023.12.04 - workaround IO.pread() not available on windows
 2021.02.18 - updated gems; changed open-uri to URI.open; enabled SSL on https://pedump.me/
 2020.08.09 - CLI: added resource extracting with --extract ID
 2020.07.28 - 0.6.1; better RICH HDR parsing/output
diff --git a/lib/pedump/cli.rb b/lib/pedump/cli.rb
index ac4af85..151cb93 100644
--- a/lib/pedump/cli.rb
+++ b/lib/pedump/cli.rb
@@ -118,6 +118,10 @@ def run
         @actions << [:va2file, va]
       end
 
+      opts.on "--set-os-version VER", "Patch OS version in PE header" do |ver|
+        @actions << [:set_os_version, ver]
+      end
+
       opts.separator ''
 
       opts.on "-W", "--web", "Uploads files to a #{URL_BASE}","for a nice HTML tables with image previews,","candies & stuff" do
@@ -337,6 +341,8 @@ def dump_action action, f
         return
       when :extract
         return extract action[1]
+      when :set_os_version
+        return set_os_version action[1]
       when :va2file
         @pedump.sections(f)
         va = action[1] =~ /(^0x)|(h$)/i ? action[1].to_i(16) : action[1].to_i
@@ -914,6 +920,40 @@ def extract_section id
     _copy_stream @pedump.io, $stdout, section.SizeOfRawData, section.PointerToRawData
   end
 
+  def set_os_version ver
+    raise "[!] invalid version #{ver.inspect}" unless ver =~ /\A(\d+)\.(\d+)\Z/
+    raise "[!] no IMAGE_OPTIONAL_HEADER" if @pedump.pe.ifh.SizeOfOptionalHeader.to_i == 0
+    major = $1.to_i
+    minor = $2.to_i
+    ver = "#{major}.#{minor}"
+    ioh = @pedump.pe.image_optional_header
+
+    prev_os_ver = "#{ioh.MajorOperatingSystemVersion}.#{ioh.MinorOperatingSystemVersion}"
+    prev_ss_ver = "#{ioh.MajorSubsystemVersion}.#{ioh.MinorSubsystemVersion}"
+
+    if prev_os_ver == ver && prev_ss_ver == ver
+      @pedump.logger.warn "[?] already has #{ver}"
+      return
+    end
+
+    if prev_os_ver != ver
+      ioh.MajorOperatingSystemVersion = major
+      ioh.MinorOperatingSystemVersion = minor
+      @pedump.logger.warn "[.] MajorOperatingSystemVersion: #{prev_os_ver} -> #{ver}"
+    end
+
+    if prev_ss_ver != ver
+      ioh.MajorSubsystemVersion = major
+      ioh.MinorSubsystemVersion = minor
+      @pedump.logger.warn "[.] MajorSubsystemVersion:       #{prev_ss_ver} -> #{ver}"
+    end
+
+    io = @pedump.io.reopen(@file_name,'rb+')
+    io.seek @pedump.pe.ioh_offset
+    io.write ioh.pack
+    io.close
+  end
+
   private
 
   # https://github.com/zed-0xff/pedump/issues/44
diff --git a/lib/pedump/pe.rb b/lib/pedump/pe.rb
index 4914c55..aae4132 100644
--- a/lib/pedump/pe.rb
+++ b/lib/pedump/pe.rb
@@ -7,6 +7,8 @@ class PE < Struct.new(
     :image_optional_header, # includes data directory
     :section_table
   )
+    attr_accessor :ioh_offset
+
     alias :ifh       :image_file_header
     alias :ifh=      :image_file_header=
     alias :ioh       :image_optional_header
@@ -68,7 +70,7 @@ def self.read f, args = {}
       end
       pe = PE.new(pe_sig)
       pe.image_file_header = IMAGE_FILE_HEADER.read(f)
-      ioh_offset = f.tell # offset to IMAGE_OPTIONAL_HEADER
+      pe.ioh_offset = f.tell # offset to IMAGE_OPTIONAL_HEADER
       if pe.ifh.SizeOfOptionalHeader.to_i > 0
         if pe.x64?
           pe.image_optional_header = IMAGE_OPTIONAL_HEADER64.read(f, pe.ifh.SizeOfOptionalHeader)
@@ -81,7 +83,7 @@ def self.read f, args = {}
 
       # The Windows loader expects to find the PE section headers after the optional header. It calculates the address of the first section header by adding SizeOfOptionalHeader to the beginning of the optional header.
       # // http://www.phreedom.org/research/tinype/
-      f.seek( ioh_offset + pe.ifh.SizeOfOptionalHeader.to_i )
+      f.seek( pe.ioh_offset + pe.ifh.SizeOfOptionalHeader.to_i )
       pe.sections = read_sections(f, nToRead, args)
 
       pe_end = f.tell