diff --git a/include/dwarfs/format.h b/include/dwarfs/format.h
new file mode 100644
index 00000000..bf8d43ee
--- /dev/null
+++ b/include/dwarfs/format.h
@@ -0,0 +1,34 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/**
+ * \author     Marcus Holland-Moritz (github@mhxnet.de)
+ * \copyright  Copyright (c) Marcus Holland-Moritz
+ *
+ * This file is part of dwarfs.
+ *
+ * dwarfs is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * dwarfs is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with dwarfs.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <fmt/format.h>
+
+template <typename T, typename U>
+struct fmt::formatter<std::pair<T, U>> {
+ public:
+  constexpr auto parse(format_parse_context& ctx) { return ctx.begin(); }
+  template <typename Context>
+  constexpr auto format(std::pair<T, U> const& foo, Context& ctx) const {
+    return fmt::format_to(ctx.out(), "({}, {})", foo.first, foo.second);
+  }
+};
diff --git a/src/dwarfs/file_scanner.cpp b/src/dwarfs/file_scanner.cpp
index f6d30faa..b2085acc 100644
--- a/src/dwarfs/file_scanner.cpp
+++ b/src/dwarfs/file_scanner.cpp
@@ -28,8 +28,6 @@
 #include <folly/String.h>
 #include <folly/container/F14Map.h>
 
-#include <fmt/format.h>
-
 #include <nlohmann/json.hpp>
 
 #include <range/v3/view/drop.hpp>
@@ -37,6 +35,7 @@
 #include <dwarfs/checksum.h>
 #include <dwarfs/entry.h>
 #include <dwarfs/file_scanner.h>
+#include <dwarfs/format.h>
 #include <dwarfs/inode.h>
 #include <dwarfs/inode_manager.h>
 #include <dwarfs/internal/worker_group.h>
@@ -47,16 +46,6 @@
 #include <dwarfs/progress.h>
 #include <dwarfs/util.h>
 
-template <typename T, typename U>
-class fmt::formatter<std::pair<T, U>> {
- public:
-  constexpr auto parse(format_parse_context& ctx) { return ctx.begin(); }
-  template <typename Context>
-  constexpr auto format(std::pair<T, U> const& foo, Context& ctx) const {
-    return fmt::format_to(ctx.out(), "({}, {})", foo.first, foo.second);
-  }
-};
-
 namespace dwarfs::detail {
 
 namespace {