diff --git a/cli/cmdlineparser.cpp b/cli/cmdlineparser.cpp
index dc8a90063..df9bd3204 100644
--- a/cli/cmdlineparser.cpp
+++ b/cli/cmdlineparser.cpp
@@ -198,6 +198,10 @@ bool CmdLineParser::fillSettingsFromArgs(int argc, const char* const argv[])
     assert(!(!pathnamesRef.empty() && !fileSettingsRef.empty()));
 
     if (!fileSettingsRef.empty()) {
+        // TODO: handle ignored?
+
+        // TODO: de-duplicate
+
         std::list<FileSettings> fileSettings;
         if (!mSettings.fileFilters.empty()) {
             // filter only for the selected filenames from all project files
@@ -244,6 +248,19 @@ bool CmdLineParser::fillSettingsFromArgs(int argc, const char* const argv[])
             }
         }
 
+        // de-duplicate files
+        {
+            auto it = filesResolved.begin();
+            while (it != filesResolved.end()) {
+                const std::string& name = it->first;
+                // TODO: log if duplicated files were dropped
+                filesResolved.erase(std::remove_if(std::next(it), filesResolved.end(), [&](const std::pair<std::string, std::size_t>& entry) {
+                    return entry.first == name;
+                }), filesResolved.end());
+                ++it;
+            }
+        }
+
         std::list<std::pair<std::string, std::size_t>> files;
         if (!mSettings.fileFilters.empty()) {
             std::copy_if(filesResolved.cbegin(), filesResolved.cend(), std::inserter(files, files.end()), [&](const decltype(filesResolved)::value_type& entry) {
diff --git a/test/cli/test-more-projects.py b/test/cli/test-more-projects.py
index 3693f930d..d84ff8746 100644
--- a/test/cli/test-more-projects.py
+++ b/test/cli/test-more-projects.py
@@ -432,3 +432,75 @@ def test_project_file_order(tmpdir):
         '4/4 files checked 0% done'
     ]
     assert stderr == ''
+
+
+def test_project_file_duplicate(tmpdir):
+    test_file_a = os.path.join(tmpdir, 'a.c')
+    with open(test_file_a, 'wt'):
+        pass
+
+    project_file = os.path.join(tmpdir, 'test.cppcheck')
+    with open(project_file, 'wt') as f:
+        f.write(
+            """<?xml version="1.0" encoding="UTF-8"?>
+<project>
+    <paths>
+        <dir name="{}"/>
+        <dir name="{}"/>
+        <dir name="{}"/>
+    </paths>
+</project>""".format(test_file_a, test_file_a, tmpdir))
+
+    args = ['--project={}'.format(project_file)]
+
+    exitcode, stdout, stderr = cppcheck(args)
+    assert exitcode == 0
+    lines = stdout.splitlines()
+    assert lines == [
+        'Checking {} ...'.format(test_file_a)
+    ]
+    assert stderr == ''
+
+
+def test_project_file_duplicate_2(tmpdir):
+    test_file_a = os.path.join(tmpdir, 'a.c')
+    with open(test_file_a, 'wt'):
+        pass
+    test_file_b = os.path.join(tmpdir, 'b.c')
+    with open(test_file_b, 'wt'):
+        pass
+    test_file_c = os.path.join(tmpdir, 'c.c')
+    with open(test_file_c, 'wt'):
+        pass
+
+    project_file = os.path.join(tmpdir, 'test.cppcheck')
+    with open(project_file, 'wt') as f:
+        f.write(
+            """<?xml version="1.0" encoding="UTF-8"?>
+<project>
+    <paths>
+        <dir name="{}"/>
+        <dir name="{}"/>
+        <dir name="{}"/>
+        <dir name="{}"/>
+        <dir name="{}"/>
+        <dir name="{}"/>
+        <dir name="{}"/>
+        <dir name="{}"/>
+    </paths>
+</project>""".format(test_file_c, test_file_a, test_file_b, tmpdir, test_file_b, test_file_c, test_file_a, tmpdir))
+
+    args = ['--project={}'.format(project_file)]
+
+    exitcode, stdout, stderr = cppcheck(args)
+    assert exitcode == 0
+    lines = stdout.splitlines()
+    assert lines == [
+        'Checking {} ...'.format(test_file_c),
+        '1/3 files checked 0% done',
+        'Checking {} ...'.format(test_file_a),
+        '2/3 files checked 0% done',
+        'Checking {} ...'.format(test_file_b),
+        '3/3 files checked 0% done'
+    ]
+    assert stderr == ''
diff --git a/test/cli/test-other.py b/test/cli/test-other.py
index a689bc92c..0ad6573f6 100644
--- a/test/cli/test-other.py
+++ b/test/cli/test-other.py
@@ -782,3 +782,46 @@ Line 6
   0 always 0
 '''.format(test_file_cpp, test_file_h_2, test_file_h, test_file_cpp, test_file_h_2, test_file_h, test_file_cpp)
     assert stderr == ''
+
+
+def test_file_duplicate(tmpdir):
+    test_file_a = os.path.join(tmpdir, 'a.c')
+    with open(test_file_a, 'wt'):
+        pass
+
+    args = [test_file_a, test_file_a, str(tmpdir)]
+
+    exitcode, stdout, stderr = cppcheck(args)
+    assert exitcode == 0
+    lines = stdout.splitlines()
+    assert lines == [
+        'Checking {} ...'.format(test_file_a)
+    ]
+    assert stderr == ''
+
+
+def test_file_duplicate_2(tmpdir):
+    test_file_a = os.path.join(tmpdir, 'a.c')
+    with open(test_file_a, 'wt'):
+        pass
+    test_file_b = os.path.join(tmpdir, 'b.c')
+    with open(test_file_b, 'wt'):
+        pass
+    test_file_c = os.path.join(tmpdir, 'c.c')
+    with open(test_file_c, 'wt'):
+        pass
+
+    args = [test_file_c, test_file_a, test_file_b, str(tmpdir), test_file_b, test_file_c, test_file_a, str(tmpdir)]
+
+    exitcode, stdout, stderr = cppcheck(args)
+    assert exitcode == 0
+    lines = stdout.splitlines()
+    assert lines == [
+        'Checking {} ...'.format(test_file_c),
+        '1/3 files checked 0% done',
+        'Checking {} ...'.format(test_file_a),
+        '2/3 files checked 0% done',
+        'Checking {} ...'.format(test_file_b),
+        '3/3 files checked 0% done'
+    ]
+    assert stderr == ''