diff --git a/cli/cmdlineparser.cpp b/cli/cmdlineparser.cpp
index 173e63133..4754bf4b4 100644
--- a/cli/cmdlineparser.cpp
+++ b/cli/cmdlineparser.cpp
@@ -665,7 +665,6 @@ bool CmdLineParser::parseFromArgs(int argc, const char* const argv[])
                 ImportProject::Type projType = mSettings.project.import(projectFile, &mSettings);
                 mSettings.project.projectType = projType;
                 if (projType == ImportProject::Type::CPPCHECK_GUI) {
-                    mPathNames = mSettings.project.guiProject.pathNames;
                     for (const std::string &lib : mSettings.project.guiProject.libraries)
                         mSettings.libraries.emplace_back(lib);
 
@@ -1032,12 +1031,20 @@ bool CmdLineParser::parseFromArgs(int argc, const char* const argv[])
         return true;
     }
 
+    if (!mPathNames.empty() && mSettings.project.projectType != ImportProject::Type::NONE) {
+        mLogger.printError("--project cannot be used in conjunction with source files.");
+        return false;
+    }
+
     // Print error only if we have "real" command and expect files
-    if (!mExitAfterPrint && mPathNames.empty() && mSettings.project.fileSettings.empty()) {
+    if (!mExitAfterPrint && mPathNames.empty() && mSettings.project.guiProject.pathNames.empty() && mSettings.project.fileSettings.empty()) {
         mLogger.printError("no C or C++ source files found.");
         return false;
     }
 
+    if (!mSettings.project.guiProject.pathNames.empty())
+        mPathNames = mSettings.project.guiProject.pathNames;
+
     // Use paths _pathnames if no base paths for relative path output are given
     if (mSettings.basePaths.empty() && mSettings.relativePaths)
         mSettings.basePaths = mPathNames;
diff --git a/releasenotes.txt b/releasenotes.txt
index b0b87e6db..bda7ad136 100644
--- a/releasenotes.txt
+++ b/releasenotes.txt
@@ -20,4 +20,5 @@ Other:
 - The undocumented and deprecated command-line options `--template <template>` and `--template-format <template>` has been removed. Please use `--template=` and `--template-format=` instead.
 - "--showtime=summary" will now show a single summary at the end instead of showing it after each file when using the thread execution (default on Windows)
 - added "--showtime=none" to disable any previously specified showtime report. "--showtime=" without parameter is no longer valid.
-- Multiple "--project" options are now prohibited. These would have overlapped each other and leads to unexpected behavior. Please use separate runs with a single "--project" option instead.
+- Multiple "--project" options are now prohibited. These would have overlapped each other and lead to unexpected behavior. Please use separate runs with a single "--project" option instead.
+- "--project" can also no longer be used in conjunction with additional source files.
diff --git a/test/testcmdlineparser.cpp b/test/testcmdlineparser.cpp
index deed0ed97..18cad8e60 100644
--- a/test/testcmdlineparser.cpp
+++ b/test/testcmdlineparser.cpp
@@ -283,8 +283,10 @@ private:
         TEST_CASE(templateMaxTime);
         TEST_CASE(project);
         TEST_CASE(projectMultiple);
+        TEST_CASE(projectAndSource);
         TEST_CASE(projectEmpty);
         TEST_CASE(projectMissing);
+        TEST_CASE(projectNoPaths);
 
         TEST_CASE(ignorepaths1);
         TEST_CASE(ignorepaths2);
@@ -1952,10 +1954,18 @@ private:
 
     void project() {
         REDIRECT;
-        ScopedFile file("project.cppcheck", "<project></project>");
-        const char * const argv[] = {"cppcheck", "--project=project.cppcheck", "file.cpp"};
-        ASSERT(parser->parseFromArgs(3, argv));
+        ScopedFile file("project.cppcheck",
+                        "<project>\n"
+                        "<paths>\n"
+                        "<dir name=\"dir\"/>\n"
+                        "</paths>\n"
+                        "</project>");
+        const char * const argv[] = {"cppcheck", "--project=project.cppcheck"};
+        ASSERT(parser->parseFromArgs(2, argv));
         ASSERT_EQUALS(static_cast<int>(ImportProject::Type::CPPCHECK_GUI), static_cast<int>(settings->project.projectType));
+        ASSERT_EQUALS(1, parser->getPathNames().size());
+        auto it = parser->getPathNames().cbegin();
+        ASSERT_EQUALS("dir", *it);
         ASSERT_EQUALS("", logger->str());
     }
 
@@ -1967,6 +1977,14 @@ private:
         ASSERT_EQUALS("cppcheck: error: multiple --project options are not supported.\n", logger->str());
     }
 
+    void projectAndSource() {
+        REDIRECT;
+        ScopedFile file("project.cppcheck", "<project></project>");
+        const char * const argv[] = {"cppcheck", "--project=project.cppcheck", "file.cpp"};
+        ASSERT(!parser->parseFromArgs(3, argv));
+        ASSERT_EQUALS("cppcheck: error: --project cannot be used in conjunction with source files.\n", logger->str());
+    }
+
     void projectEmpty() {
         REDIRECT;
         const char * const argv[] = {"cppcheck", "--project=", "file.cpp"};
@@ -1981,6 +1999,13 @@ private:
         ASSERT_EQUALS("cppcheck: error: failed to open project 'project.cppcheck'. The file does not exist.\n", logger->str());
     }
 
+    void projectNoPaths() {
+        ScopedFile file("project.cppcheck", "<project></project>");
+        const char * const argv[] = {"cppcheck", "--project=project.cppcheck"};
+        ASSERT(!parser->parseFromArgs(2, argv));
+        ASSERT_EQUALS("cppcheck: error: no C or C++ source files found.\n", logger->str());
+    }
+
     void ignorepaths1() {
         REDIRECT;
         const char * const argv[] = {"cppcheck", "-isrc", "file.cpp"};