diff --git a/dumux/io/format.hh b/dumux/io/format.hh
index f0b2547a5e7c15fc0a6bd873cbb245b1c3d84d4e..bccf607c1db8c8365c851111f4bcf153279ccd5d 100644
--- a/dumux/io/format.hh
+++ b/dumux/io/format.hh
@@ -36,10 +36,10 @@
 //! Formatting tools in the style of std::format (C++20)
 namespace Dumux::Fmt {
 
-using fmt::format;
-using fmt::format_to;
-using fmt::format_to_n;
-using fmt::formatted_size;
+using Dumux::Detail::fmt::format;
+using Dumux::Detail::fmt::format_to;
+using Dumux::Detail::fmt::format_to_n;
+using Dumux::Detail::fmt::formatted_size;
 
 } // end namespace Dumux::Fmt
 
diff --git a/dumux/io/format/fmt/core.h b/dumux/io/format/fmt/core.h
index 2903be5a0715dfdf210e8826b507eab1684e0c5b..7c5fdc7067359cc670e23960888050dc3c3e9691 100644
--- a/dumux/io/format/fmt/core.h
+++ b/dumux/io/format/fmt/core.h
@@ -5,8 +5,8 @@
 //
 // For the license information refer to format.h.
 
-#ifndef FMT_CORE_H_
-#define FMT_CORE_H_
+#ifndef DUMUX_FMT_CORE_H_
+#define DUMUX_FMT_CORE_H_
 
 #include <cstdio>  // std::FILE
 #include <cstring>
@@ -201,7 +201,7 @@
       }
 #  endif
 #  define FMT_BEGIN_NAMESPACE \
-    namespace fmt {           \
+    namespace Dumux::Detail::fmt {           \
     FMT_INLINE_NAMESPACE v7 {
 #endif
 
@@ -292,7 +292,7 @@ FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
 #    define FMT_ASSERT(condition, message)                                    \
       ((condition) /* void() fails with -Winvalid-constexpr on clang 4.0.1 */ \
            ? (void)0                                                          \
-           : ::fmt::detail::assert_fail(__FILE__, __LINE__, (message)))
+           : Dumux::Detail::fmt::detail::assert_fail(__FILE__, __LINE__, (message)))
 #  endif
 #endif
 
diff --git a/dumux/io/format/fmt/format-inl.h b/dumux/io/format/fmt/format-inl.h
index b7cb3209c855e261815bac4b0c268ce735e5fa29..ffc6588e2eed9df429041089542d8f32f9e8b36e 100644
--- a/dumux/io/format/fmt/format-inl.h
+++ b/dumux/io/format/fmt/format-inl.h
@@ -5,8 +5,8 @@
 //
 // For the license information refer to format.h.
 
-#ifndef FMT_FORMAT_INL_H_
-#define FMT_FORMAT_INL_H_
+#ifndef DUMUX_FMT_FORMAT_INL_H_
+#define DUMUX_FMT_FORMAT_INL_H_
 
 #include <cassert>
 #include <cctype>
@@ -29,8 +29,8 @@
 
 // Dummy implementations of strerror_r and strerror_s called if corresponding
 // system functions are not available.
-inline fmt::detail::null<> strerror_r(int, char*, ...) { return {}; }
-inline fmt::detail::null<> strerror_s(char*, size_t, ...) { return {}; }
+inline Dumux::Detail::fmt::detail::null<> strerror_r(int, char*, ...) { return {}; }
+inline Dumux::Detail::fmt::detail::null<> strerror_s(char*, size_t, ...) { return {}; }
 
 FMT_BEGIN_NAMESPACE
 namespace detail {
diff --git a/dumux/io/format/fmt/format.h b/dumux/io/format/fmt/format.h
index fbe5045068575481dd5eb8877705fba246bc2a52..8f024ecb8fd7f6fd91f7dd2986b28c9593d43400 100644
--- a/dumux/io/format/fmt/format.h
+++ b/dumux/io/format/fmt/format.h
@@ -30,8 +30,8 @@
  without including the above copyright and permission notices.
  */
 
-#ifndef FMT_FORMAT_H_
-#define FMT_FORMAT_H_
+#ifndef DUMUX_FMT_FORMAT_H_
+#define DUMUX_FMT_FORMAT_H_
 
 #include <algorithm>
 #include <cerrno>
diff --git a/dumux/io/format/fmt/ranges.h b/dumux/io/format/fmt/ranges.h
index b603d637d74b3d2aea6477b2c201d5c232cf304e..86361c54db3dcd78386790ecd1ec0a692c6b5830 100644
--- a/dumux/io/format/fmt/ranges.h
+++ b/dumux/io/format/fmt/ranges.h
@@ -9,8 +9,8 @@
 // All Rights Reserved
 // {fmt} support for ranges, containers and types tuple interface.
 
-#ifndef FMT_RANGES_H_
-#define FMT_RANGES_H_
+#ifndef DUMUX_FMT_RANGES_H_
+#define DUMUX_FMT_RANGES_H_
 
 #include <initializer_list>
 #include <type_traits>
diff --git a/test/porousmediumflow/2p/cornerpoint/main.cc b/test/porousmediumflow/2p/cornerpoint/main.cc
index e356de7c3d231b2f8754f1b10a80bd1f899d96f2..dd2aa8937c9496742f1c07093d711f0c6a4d6a51 100644
--- a/test/porousmediumflow/2p/cornerpoint/main.cc
+++ b/test/porousmediumflow/2p/cornerpoint/main.cc
@@ -48,6 +48,7 @@
 
 #include <dumux/io/vtkoutputmodule.hh>
 #include <dumux/io/grid/cpgridmanager.hh>
+#include <dumux/io/format.hh>
 
 #include "properties.hh"
 
@@ -80,6 +81,8 @@ int main(int argc, char** argv)
     // we compute on the leaf grid view
     const auto& leafGridView = gridManager.grid().leafGridView();
 
+    std::cout << Fmt::format("Initialized cornerpoint grid with {} elements\n", leafGridView.size(0));
+
     // create the finite volume grid geometry
     using GridGeometry = GetPropType<TypeTag, Properties::GridGeometry>;
     auto gridGeometry = std::make_shared<GridGeometry>(leafGridView);