diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a5e0cf6..a078b04 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,34 +16,55 @@ env:
 jobs:
 
   #
-  # Test project on Ubuntu with Intel ifx compiler
+  # Test project in various system configurations
   #
-  ubuntu-ifx:
+  fortuno-test:
 
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest]
+        compilers: [Intel, GNU]
 
     steps:
 
       - name: Check-out code
         uses: actions/checkout@v3
 
-      - name: Setup Intel oneAPI
+      - name: Setup Intel compiler
+        if: ${{ contains(matrix.compilers, 'Intel') }}
         uses: rscohn2/setup-oneapi@v0
         with:
           components: ifx
 
-      - name: Set compiler environment
+      - name: Setup Intel environment
+        if: ${{ contains(matrix.compilers, 'Intel') }}
         run: |
+          source /opt/intel/oneapi/setvars.sh
+          printenv >> ${GITHUB_ENV}
           echo "FC=ifx" >> ${GITHUB_ENV}
           echo "FPM_FC=ifx" >> ${GITHUB_ENV}
 
+      - name: Setup GNU compiler
+        if: ${{ contains(matrix.compilers, 'GNU') }}
+        uses: fortran-lang/setup-fortran@v1
+        with:
+          compiler: gcc
+          version: 13
+
+      - name: Setup GNU environment
+        if: ${{ contains(matrix.compilers, 'GNU') }}
+        run: |
+          echo "FC=${{ env.FC }}" >> ${GITHUB_ENV}
+          echo "FPM_FC=${{ env.FC }}" >> ${GITHUB_ENV}
+
       - name: Setup build tools
         run: |
           pip install cmake fpm meson ninja
 
       - name: Build Fortuno
         run: |
-          source /opt/intel/oneapi/setvars.sh
           cmake -B ${BUILD_DIR} -G Ninja -DCMAKE_INSTALL_PREFIX=${INSTALL_DIR}
           cmake --build ${BUILD_DIR}
           cmake --install ${BUILD_DIR}
@@ -51,7 +72,6 @@ jobs:
 
       - name: Test CMake export
         run: |
-          source /opt/intel/oneapi/setvars.sh
           CMAKE_PREFIX_PATH=${INSTALL_DIR} cmake -B ${BUILD_DIR} -G Ninja test/export
           cmake --build ${BUILD_DIR}
           ${BUILD_DIR}/testapp
@@ -59,27 +79,24 @@ jobs:
 
       - name: Test PkgConfig export
         run: |
-          source /opt/intel/oneapi/setvars.sh
           export LD_LIBRARY_PATH="${PWD}/${INSTALL_DIR}/lib:${LD_LIBRARY_PATH}"
           export PKG_CONFIG_PATH="${PWD}/${INSTALL_DIR}/lib/pkgconfig:${PKG_CONFIG_PATH}"
           cflags="$(pkg-config --cflags fortuno)"
           lflags="$(pkg-config --libs fortuno)"
           mkdir ${BUILD_DIR}
           pushd ${BUILD_DIR}
-          ifx  ${cflags} ${lflags} -o testapp ../test/export/app/testapp.f90
+          ${FC} ${cflags} -o testapp ../test/export/app/testapp.f90 ${lflags}
           ./testapp
           popd
           rm -rf ${BUILD_DIR}
 
       - name: Test fpm export
         run: |
-          source /opt/intel/oneapi/setvars.sh
           cd test/export
           fpm run testapp
 
       - name: Test meson PkgConfig export
         run: |
-          source /opt/intel/oneapi/setvars.sh
           export PKG_CONFIG_PATH="${PWD}/${INSTALL_DIR}/lib/pkgconfig:${PKG_CONFIG_PATH}"
           cd test/export
           meson setup -Dfortuno_subproject=false ${BUILD_DIR}
@@ -89,7 +106,6 @@ jobs:
 
       - name: Test meson subproject export
         run: |
-          source /opt/intel/oneapi/setvars.sh
           FORTUNO_DIR=${PWD}
           GIT_REV=$(git rev-parse HEAD)
           cd test/export
diff --git a/src/fortuno/argumentparser.f90 b/src/fortuno/argumentparser.f90
index ce180f4..1c792a8 100644
--- a/src/fortuno/argumentparser.f90
+++ b/src/fortuno/argumentparser.f90
@@ -130,6 +130,8 @@ subroutine argument_parser_parse_args(this, argumentvalues, logger, exitcode)
     allocate(argumentvalues%argvals(0))
     allocate(posargs(0))
     optionsallowed = .true.
+
+    ! Process all arguments
     iarg = 0
     argloop: do while (iarg < nargs)
       iarg = iarg + 1
@@ -183,10 +185,20 @@ subroutine argument_parser_parse_args(this, argumentvalues, logger, exitcode)
         return
       end associate
     end do argloop
+
+    ! Check collected positional arguments
     associate (argdef => this%argdefs(nargdefs))
+      ! If the last argdef was not an option, store all position arguments under this name
       if (.not. allocated(argdef%longopt) .and. argdef%shortopt == "") then
-        argumentvalues%argvals = [argumentvalues%argvals,&
-            & argument_value(name=argdef%name, argval=string_list(posargs))]
+        ! argumentvalues%argvals = [argumentvalues%argvals,&
+        !     & argument_value(name=argdef%name, argval=string_list(posargs))]
+        ! Workaround:gfortran:13.2
+        block
+          class(*), allocatable :: tmp
+          tmp = string_list(posargs)
+          argumentvalues%argvals = [argumentvalues%argvals,&
+              & argument_value(name=argdef%name, argval=tmp)]
+        end block
       else if (size(posargs) > 1) then
         call logger%log_error("Superfluous positional arguments found")
         exitcode = 1