diff --git a/.github/workflows/gcc11.yml b/.github/workflows/gcc11.yml
new file mode 100644
index 0000000..e82094f
--- /dev/null
+++ b/.github/workflows/gcc11.yml
@@ -0,0 +1,29 @@
+name: gcc 11
+
+on: [push, pull_request]
+
+
+jobs:
+  build:
+    name: Compiles with gcc 11
+    runs-on: ubuntu-20.04
+
+    steps:
+    - name: checkout
+      uses: actions/checkout@v2
+    - name: install packages
+      run: sudo apt install build-essential nettle-dev time gcc-11 g++-11
+    - name: bootstrap
+      run: ./bootstrap.sh
+    - name: configure
+      run: ./configure CXX=g++-11
+    - name: build
+      run: make
+    - name: check
+      run: make check
+    - name: store the logs as an artifact
+      if: ${{ always() }}
+      uses: actions/upload-artifact@v2.2.4
+      with:
+         path: '**/*.log'
+
diff --git a/lgtm.yml b/lgtm.yml
index 6b1ff87..a159312 100644
--- a/lgtm.yml
+++ b/lgtm.yml
@@ -6,6 +6,5 @@ extraction:
           - nettle-dev
      configure:
         command:
-          - grep -v AX_CXX_COMPILE_STDCXX <configure.ac >tmp && mv tmp configure.ac
           - ./bootstrap.sh
           - ./configure
diff --git a/rdfind.cc b/rdfind.cc
index fbd6cb8..cd35314 100644
--- a/rdfind.cc
+++ b/rdfind.cc
@@ -9,6 +9,7 @@
 // std
 #include <algorithm>
 #include <iostream>
+#include <limits>
 #include <string>
 #include <vector>
 
@@ -60,7 +61,7 @@ usage()
     << " -followsymlinks    true |(false) follow symlinks\n"
     << " -removeidentinode (true)| false  ignore files with nonunique "
        "device and inode\n"
-    << " -checksum           md5 |(sha1)| sha256\n"
+    << " -checksum           md5 |(sha1)| sha256 | none\n"
     << "                                  checksum type\n"
     << " -deterministic    (true)| false  makes results independent of order\n"
     << "                                  from listing the filesystem\n"
@@ -102,6 +103,7 @@ struct Options
   bool followsymlinks = false;        // follow symlinks
   bool dryrun = false;                // only dryrun, don't destroy anything
   bool remove_identical_inode = true; // remove files with identical inodes
+  bool checksum = true;      // use some checksum
   bool usemd5 = false;       // use md5 checksum to check for similarity
   bool usesha1 = false;      // use sha1 checksum to check for similarity
   bool usesha256 = false;    // use sha256 checksum to check for similarity
@@ -173,8 +175,10 @@ parseOptions(Parser& parser)
         o.usesha1 = true;
       } else if (parser.parsed_string_is("sha256")) {
         o.usesha256 = true;
+      } else if (parser.parsed_string_is("none")) {
+        o.checksum = false;
       } else {
-        std::cerr << "expected md5/sha1/sha256, not \""
+        std::cerr << "expected md5/sha1/sha256/none, not \""
                   << parser.get_parsed_string() << "\"\n";
         std::exit(EXIT_FAILURE);
       }
@@ -236,8 +240,10 @@ parseOptions(Parser& parser)
   // done with parsing of options. remaining arguments are files and dirs.
 
   // decide what checksum to use - if no checksum is set, force sha1!
-  if (!o.usemd5 && !o.usesha1 && !o.usesha256) {
-    o.usesha1 = true;
+  if (o.checksum) {
+    if (!o.usemd5 && !o.usesha1 && !o.usesha256) {
+      o.usesha1 = true;
+    }
   }
   return o;
 }
@@ -355,17 +361,19 @@ main(int narg, const char* argv[])
     { Fileinfo::readtobuffermode::READ_FIRST_BYTES, "first bytes" },
     { Fileinfo::readtobuffermode::READ_LAST_BYTES, "last bytes" },
   };
-  if (o.usemd5) {
-    modes.emplace_back(Fileinfo::readtobuffermode::CREATE_MD5_CHECKSUM,
-                       "md5 checksum");
-  }
-  if (o.usesha1) {
-    modes.emplace_back(Fileinfo::readtobuffermode::CREATE_SHA1_CHECKSUM,
-                       "sha1 checksum");
-  }
-  if (o.usesha256) {
-    modes.emplace_back(Fileinfo::readtobuffermode::CREATE_SHA256_CHECKSUM,
-                       "sha256 checksum");
+  if (o.checksum) {
+    if (o.usemd5) {
+      modes.emplace_back(Fileinfo::readtobuffermode::CREATE_MD5_CHECKSUM,
+                         "md5 checksum");
+    }
+    if (o.usesha1) {
+      modes.emplace_back(Fileinfo::readtobuffermode::CREATE_SHA1_CHECKSUM,
+                         "sha1 checksum");
+    }
+    if (o.usesha256) {
+      modes.emplace_back(Fileinfo::readtobuffermode::CREATE_SHA256_CHECKSUM,
+                         "sha256 checksum");
+    }
   }
 
   for (auto it = modes.begin() + 1; it != modes.end(); ++it) {