diff --git a/common/CMakeLists.txt b/common/CMakeLists.txt
index 570dd57a1..e43c0da97 100644
--- a/common/CMakeLists.txt
+++ b/common/CMakeLists.txt
@@ -1,5 +1,5 @@
 ## CMakeLists.txt
-# 
+#
 # Author: Steffen Vogel <post@steffenvogel.de>
 # SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
 # SPDX-License-Identifier: Apache-2.0
@@ -42,13 +42,18 @@ endif()
 find_package(OpenSSL 1.0.0 REQUIRED)
 find_package(CURL 7.29 REQUIRED)
 find_package(spdlog 1.6.0 REQUIRED)
-find_package(fmt 5.3.0 REQUIRED)
+find_package(fmt 6.0.0 REQUIRED)
 find_package(Criterion)
 
 pkg_check_modules(JANSSON IMPORTED_TARGET REQUIRED jansson>=2.7)
 pkg_check_modules(LIBCONFIG IMPORTED_TARGET libconfig>=1.4.9)
 pkg_check_modules(UUID IMPORTED_TARGET REQUIRED uuid>=2.23)
 
+if(fmt_VERSION VERSION_LESS "9.0.0")
+    message("Using legacy ostream formatting")
+    set(FMT_LEGACY_OSTREAM_FORMATTER 1)
+endif()
+
 add_subdirectory(lib)
 if(CRITERION_FOUND AND TOPLEVEL_PROJECT)
     add_subdirectory(tests)
diff --git a/common/include/villas/config.hpp.in b/common/include/villas/config.hpp.in
index 7d667bee3..63235af35 100644
--- a/common/include/villas/config.hpp.in
+++ b/common/include/villas/config.hpp.in
@@ -47,3 +47,6 @@
 #define LOG_HEIGHT		25
 
 #cmakedefine LOG_COLOR_DISABLE
+
+// Library Features
+#cmakedefine FMT_LEGACY_OSTREAM_FORMATTER
diff --git a/common/include/villas/exceptions.hpp b/common/include/villas/exceptions.hpp
index 93677cdd2..e910dacd2 100644
--- a/common/include/villas/exceptions.hpp
+++ b/common/include/villas/exceptions.hpp
@@ -48,21 +48,17 @@ public:
 class JsonError : public std::runtime_error {
 
 protected:
-  const json_t *setting;
   json_error_t error;
 
 public:
   template <typename... Args>
   JsonError(const json_t *s, const json_error_t &e,
             const std::string &what = std::string(), Args &&...args)
-      : std::runtime_error(fmt::format(what, std::forward<Args>(args)...)),
-        setting(s), error(e) {}
-
-  virtual const char *what() const noexcept {
-    return fmt::format("{}: {} in {}:{}:{}", std::runtime_error::what(),
-                       error.text, error.source, error.line, error.column)
-        .c_str();
-  }
+      : std::runtime_error(
+            fmt::format("{}: {} in {}:{}:{}",
+                        fmt::format(what, std::forward<Args>(args)...),
+                        error.text, error.source, error.line, error.column)),
+        error(e) {}
 };
 
 class ConfigError : public std::runtime_error {
diff --git a/common/include/villas/graph/edge.hpp b/common/include/villas/graph/edge.hpp
index 7b17a2f80..6beaf9137 100644
--- a/common/include/villas/graph/edge.hpp
+++ b/common/include/villas/graph/edge.hpp
@@ -7,6 +7,8 @@
 
 #pragma once
 
+#include <fmt/ostream.h>
+#include <villas/config.hpp>
 #include <villas/graph/vertex.hpp>
 
 namespace villas {
@@ -42,3 +44,9 @@ private:
 
 } // namespace graph
 } // namespace villas
+
+#ifndef FMT_LEGACY_OSTREAM_FORMATTER
+template <>
+class fmt::formatter<villas::graph::Edge>
+    : public fmt::ostream_formatter {};
+#endif
diff --git a/common/include/villas/graph/vertex.hpp b/common/include/villas/graph/vertex.hpp
index ba65e2228..71a9f9c3d 100644
--- a/common/include/villas/graph/vertex.hpp
+++ b/common/include/villas/graph/vertex.hpp
@@ -7,6 +7,11 @@
 
 #pragma once
 
+#include <list>
+#include <sstream>
+#include <fmt/ostream.h>
+#include <villas/config.hpp>
+
 namespace villas {
 namespace graph {
 
@@ -40,3 +45,9 @@ private:
 
 } // namespace graph
 } // namespace villas
+
+#ifndef FMT_LEGACY_OSTREAM_FORMATTER
+template <>
+class fmt::formatter<villas::graph::Vertex>
+    : public fmt::ostream_formatter {};
+#endif
diff --git a/common/include/villas/log.hpp b/common/include/villas/log.hpp
index b61ec611a..0cc62775e 100644
--- a/common/include/villas/log.hpp
+++ b/common/include/villas/log.hpp
@@ -11,7 +11,6 @@
 #include <list>
 #include <string>
 
-#include <spdlog/fmt/ostr.h>
 #include <spdlog/sinks/dist_sink.h>
 #include <spdlog/sinks/stdout_color_sinks.h>
 #include <spdlog/spdlog.h>
diff --git a/common/include/villas/memory_manager.hpp b/common/include/villas/memory_manager.hpp
index 381548e54..275d5a9fa 100644
--- a/common/include/villas/memory_manager.hpp
+++ b/common/include/villas/memory_manager.hpp
@@ -12,7 +12,8 @@
 #include <stdexcept>
 #include <string>
 #include <unistd.h>
-
+#include <fmt/ostream.h>
+#include <villas/config.hpp>
 #include <villas/graph/directed.hpp>
 #include <villas/log.hpp>
 
@@ -222,3 +223,15 @@ private:
 };
 
 } // namespace villas
+
+#ifndef FMT_LEGACY_OSTREAM_FORMATTER
+template <>
+class fmt::formatter<villas::MemoryTranslation>
+    : public fmt::ostream_formatter {};
+template <>
+class fmt::formatter<villas::MemoryManager::Mapping>
+    : public fmt::ostream_formatter {};
+template <>
+class fmt::formatter<villas::MemoryManager::AddressSpaceId>
+    : public fmt::ostream_formatter {};
+#endif
diff --git a/common/include/villas/plugin.hpp b/common/include/villas/plugin.hpp
index 284853e3a..ea472d402 100644
--- a/common/include/villas/plugin.hpp
+++ b/common/include/villas/plugin.hpp
@@ -11,10 +11,10 @@
 #include <iostream>
 #include <jansson.h>
 #include <list>
-#include <spdlog/fmt/ostr.h>
 #include <string>
-
+#include <fmt/ostream.h>
 #include <villas/common.hpp>
+#include <villas/config.hpp>
 #include <villas/log.hpp>
 
 namespace villas {
@@ -132,9 +132,7 @@ public:
     return logger;
   }
 
-  // Custom formatter for spdlog
-  template <typename OStream>
-  friend OStream &operator<<(OStream &os, const class Plugin &p) {
+  friend std::ostream &operator<<(std::ostream &os, const class Plugin &p) {
     return os << p.getName();
   }
 };
@@ -151,3 +149,9 @@ template <typename T> void Registry::dump() {
 
 } // namespace plugin
 } // namespace villas
+
+#ifndef FMT_LEGACY_OSTREAM_FORMATTER
+template <>
+class fmt::formatter<villas::plugin::Plugin>
+    : public fmt::ostream_formatter {};
+#endif