diff --git a/Makefile b/Makefile
index 1f220b261..8e8c654a0 100644
--- a/Makefile
+++ b/Makefile
@@ -18,8 +18,9 @@ SRCS=$(shell find include -type f | sort)
 # the list of sources in the tests folder
 TESTS_SRCS=$(shell find tests -type f \( -name '*.hpp' -o -name '*.cpp' -o -name '*.cu' \) -not -path 'tests/thirdparty/*' -not -path 'tests/abi/include/nlohmann/*' | sort)
 
-# the single header (amalgamated from the source files)
+# the single headers (amalgamated from the source files)
 AMALGAMATED_FILE=single_include/nlohmann/json.hpp
+AMALGAMATED_FWD_FILE=single_include/nlohmann/json_fwd.hpp
 
 
 ##########################################################################
@@ -28,7 +29,7 @@ AMALGAMATED_FILE=single_include/nlohmann/json.hpp
 
 # main target
 all:
-	@echo "amalgamate - amalgamate file single_include/nlohmann/json.hpp from the include/nlohmann sources"
+	@echo "amalgamate - amalgamate files single_include/nlohmann/json{,_fwd}.hpp from the include/nlohmann sources"
 	@echo "ChangeLog.md - generate ChangeLog file"
 	@echo "check-amalgamation - check whether sources have been amalgamated"
 	@echo "clean - remove built files"
@@ -144,9 +145,9 @@ pvs_studio:
 # call the Artistic Style pretty printer on all source files
 pretty:
 	astyle \
-		--style=allman \
-		--indent=spaces=4 \
-		--indent-modifiers \
+	    --style=allman \
+	    --indent=spaces=4 \
+	    --indent-modifiers \
 	    --indent-switches \
 	    --indent-preproc-block \
 	    --indent-preproc-define \
@@ -162,27 +163,34 @@ pretty:
 	    --preserve-date \
 	    --suffix=none \
 	    --formatted \
-	   $(SRCS) $(TESTS_SRCS) $(AMALGAMATED_FILE) docs/examples/*.cpp
+	   $(SRCS) $(TESTS_SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) docs/examples/*.cpp
 
 # call the Clang-Format on all source files
 pretty_format:
 	for FILE in $(SRCS) $(TESTS_SRCS) $(AMALGAMATED_FILE) docs/examples/*.cpp; do echo $$FILE; clang-format -i $$FILE; done
 
-# create single header file
-amalgamate: $(AMALGAMATED_FILE)
-
-# call the amalgamation tool and pretty print
-$(AMALGAMATED_FILE): $(SRCS)
-	tools/amalgamate/amalgamate.py -c tools/amalgamate/config.json -s . --verbose=yes
+# create single header files and pretty print
+amalgamate: $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE)
 	$(MAKE) pretty
 
+# call the amalgamation tool for json.hpp
+$(AMALGAMATED_FILE): $(SRCS)
+	tools/amalgamate/amalgamate.py -c tools/amalgamate/config_json.json -s . --verbose=yes
+
+# call the amalgamation tool for json_fwd.hpp
+$(AMALGAMATED_FWD_FILE): $(SRCS)
+	tools/amalgamate/amalgamate.py -c tools/amalgamate/config_json_fwd.json -s . --verbose=yes
+
 # check if file single_include/nlohmann/json.hpp has been amalgamated from the nlohmann sources
 # Note: this target is called by Travis
 check-amalgamation:
 	@mv $(AMALGAMATED_FILE) $(AMALGAMATED_FILE)~
+	@mv $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_FWD_FILE)~
 	@$(MAKE) amalgamate
 	@diff $(AMALGAMATED_FILE) $(AMALGAMATED_FILE)~ || (echo "===================================================================\n  Amalgamation required! Please read the contribution guidelines\n  in file .github/CONTRIBUTING.md.\n===================================================================" ; mv $(AMALGAMATED_FILE)~ $(AMALGAMATED_FILE) ; false)
+	@diff $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_FWD_FILE)~ || (echo "===================================================================\n  Amalgamation required! Please read the contribution guidelines\n  in file .github/CONTRIBUTING.md.\n===================================================================" ; mv $(AMALGAMATED_FWD_FILE)~ $(AMALGAMATED_FWD_FILE) ; false)
 	@mv $(AMALGAMATED_FILE)~ $(AMALGAMATED_FILE)
+	@mv $(AMALGAMATED_FWD_FILE)~ $(AMALGAMATED_FWD_FILE)
 
 
 ##########################################################################
diff --git a/cmake/ci.cmake b/cmake/ci.cmake
index 22cf09093..0dc3daa89 100644
--- a/cmake/ci.cmake
+++ b/cmake/ci.cmake
@@ -589,15 +589,22 @@ file(GLOB_RECURSE INDENT_FILES
     ${PROJECT_SOURCE_DIR}/docs/examples/*.cpp
 )
 
+set(include_dir ${PROJECT_SOURCE_DIR}/single_include/nlohmann)
+set(tool_dir ${PROJECT_SOURCE_DIR}/tools/amalgamate)
 add_custom_target(ci_test_amalgamation
-    COMMAND rm -fr ${PROJECT_SOURCE_DIR}/single_include/nlohmann/json.hpp~
-    COMMAND cp ${PROJECT_SOURCE_DIR}/single_include/nlohmann/json.hpp ${PROJECT_SOURCE_DIR}/single_include/nlohmann/json.hpp~
-    COMMAND ${Python3_EXECUTABLE} ${PROJECT_SOURCE_DIR}/tools/amalgamate/amalgamate.py -c ${PROJECT_SOURCE_DIR}/tools/amalgamate/config.json -s .
-    COMMAND ${ASTYLE_TOOL} ${ASTYLE_FLAGS} --suffix=none --quiet ${PROJECT_SOURCE_DIR}/single_include/nlohmann/json.hpp
-    COMMAND diff ${PROJECT_SOURCE_DIR}/single_include/nlohmann/json.hpp~ ${PROJECT_SOURCE_DIR}/single_include/nlohmann/json.hpp
+    COMMAND rm -fr ${include_dir}/json.hpp~ ${include_dir}/json_fwd.hpp~
+    COMMAND cp ${include_dir}/json.hpp ${include_dir}/json.hpp~
+    COMMAND cp ${include_dir}/json_fwd.hpp ${include_dir}/json_fwd.hpp~
+
+    COMMAND ${Python3_EXECUTABLE} ${tool_dir}/amalgamate.py -c ${tool_dir}/config_json.json -s .
+    COMMAND ${Python3_EXECUTABLE} ${tool_dir}/amalgamate.py -c ${tool_dir}/config_json_fwd.json -s .
+    COMMAND ${ASTYLE_TOOL} ${ASTYLE_FLAGS} --suffix=none --quiet ${include_dir}/json.hpp ${include_dir}/json_fwd.hpp
+
+    COMMAND diff ${include_dir}/json.hpp~ ${include_dir}/json.hpp
+    COMMAND diff ${include_dir}/json_fwd.hpp~ ${include_dir}/json_fwd.hpp
 
     COMMAND ${ASTYLE_TOOL} ${ASTYLE_FLAGS} ${INDENT_FILES}
-    COMMAND cd ${PROJECT_SOURCE_DIR} && for FILE in `find . -name '*.orig'`\; do false \; done
+    COMMAND for FILE in `find . -name '*.orig'`\; do false \; done
 
     WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
     COMMENT "Check amalgamation and indentation"
diff --git a/single_include/nlohmann/json_fwd.hpp b/single_include/nlohmann/json_fwd.hpp
new file mode 100644
index 000000000..0718f3f65
--- /dev/null
+++ b/single_include/nlohmann/json_fwd.hpp
@@ -0,0 +1,154 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.11.1
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2022 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#ifndef INCLUDE_NLOHMANN_JSON_FWD_HPP_
+#define INCLUDE_NLOHMANN_JSON_FWD_HPP_
+
+#include <cstdint> // int64_t, uint64_t
+#include <map> // map
+#include <memory> // allocator
+#include <string> // string
+#include <vector> // vector
+
+// #include <nlohmann/detail/abi_macros.hpp>
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.11.1
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2022 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+
+
+// This file contains all macro definitions affecting or depending on the ABI
+
+#ifndef JSON_SKIP_LIBRARY_VERSION_CHECK
+    #if defined(NLOHMANN_JSON_VERSION_MAJOR) && defined(NLOHMANN_JSON_VERSION_MINOR) && defined(NLOHMANN_JSON_VERSION_PATCH)
+        #if NLOHMANN_JSON_VERSION_MAJOR != 3 || NLOHMANN_JSON_VERSION_MINOR != 11 || NLOHMANN_JSON_VERSION_PATCH != 1
+            #warning "Already included a different version of the library!"
+        #endif
+    #endif
+#endif
+
+#define NLOHMANN_JSON_VERSION_MAJOR 3   // NOLINT(modernize-macro-to-enum)
+#define NLOHMANN_JSON_VERSION_MINOR 11  // NOLINT(modernize-macro-to-enum)
+#define NLOHMANN_JSON_VERSION_PATCH 1   // NOLINT(modernize-macro-to-enum)
+
+#ifndef JSON_DIAGNOSTICS
+    #define JSON_DIAGNOSTICS 0
+#endif
+
+#ifndef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
+    #define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 0
+#endif
+
+#if JSON_DIAGNOSTICS
+    #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
+#else
+    #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS
+#endif
+
+#if JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
+    #define NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON _ldvcmp
+#else
+    #define NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON
+#endif
+
+#define NLOHMANN_JSON_ABI_PREFIX_EX(major, minor, patch) \
+    json_v ## major ## _ ## minor ## _ ## patch
+#define NLOHMANN_JSON_ABI_PREFIX(major, minor, patch) \
+    NLOHMANN_JSON_ABI_PREFIX_EX(major, minor, patch)
+
+#define NLOHMANN_JSON_ABI_CONCAT_EX(a, b, c) a ## b ## c
+#define NLOHMANN_JSON_ABI_CONCAT(a, b, c) \
+    NLOHMANN_JSON_ABI_CONCAT_EX(a, b, c)
+
+#define NLOHMANN_JSON_ABI_STRING                                    \
+    NLOHMANN_JSON_ABI_CONCAT(                                       \
+            NLOHMANN_JSON_ABI_PREFIX(                               \
+                    NLOHMANN_JSON_VERSION_MAJOR,                    \
+                    NLOHMANN_JSON_VERSION_MINOR,                    \
+                    NLOHMANN_JSON_VERSION_PATCH),                   \
+            NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS,                      \
+            NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON)
+
+#ifndef NLOHMANN_JSON_NAMESPACE
+    #define NLOHMANN_JSON_NAMESPACE nlohmann::NLOHMANN_JSON_ABI_STRING
+#endif
+
+#ifndef NLOHMANN_JSON_NAMESPACE_BEGIN
+#define NLOHMANN_JSON_NAMESPACE_BEGIN         \
+    namespace nlohmann                        \
+    {                                         \
+    inline namespace NLOHMANN_JSON_ABI_STRING \
+    {
+#endif
+
+#ifndef NLOHMANN_JSON_NAMESPACE_END
+#define NLOHMANN_JSON_NAMESPACE_END \
+    }  /* namespace (abi_string) */ \
+    }  /* namespace nlohmann */
+#endif
+
+
+/*!
+@brief namespace for Niels Lohmann
+@see https://github.com/nlohmann
+@since version 1.0.0
+*/
+NLOHMANN_JSON_NAMESPACE_BEGIN
+
+/*!
+@brief default JSONSerializer template argument
+
+This serializer ignores the template arguments and uses ADL
+([argument-dependent lookup](https://en.cppreference.com/w/cpp/language/adl))
+for serialization.
+*/
+template<typename T = void, typename SFINAE = void>
+struct adl_serializer;
+
+/// a class to store JSON values
+/// @sa https://json.nlohmann.me/api/basic_json/
+template<template<typename U, typename V, typename... Args> class ObjectType =
+         std::map,
+         template<typename U, typename... Args> class ArrayType = std::vector,
+         class StringType = std::string, class BooleanType = bool,
+         class NumberIntegerType = std::int64_t,
+         class NumberUnsignedType = std::uint64_t,
+         class NumberFloatType = double,
+         template<typename U> class AllocatorType = std::allocator,
+         template<typename T, typename SFINAE = void> class JSONSerializer =
+         adl_serializer,
+         class BinaryType = std::vector<std::uint8_t>>
+class basic_json;
+
+/// @brief JSON Pointer defines a string syntax for identifying a specific value within a JSON document
+/// @sa https://json.nlohmann.me/api/json_pointer/
+template<typename RefStringType>
+class json_pointer;
+
+/*!
+@brief default specialization
+@sa https://json.nlohmann.me/api/json/
+*/
+using json = basic_json<>;
+
+/// @brief a minimal map-like container that preserves insertion order
+/// @sa https://json.nlohmann.me/api/ordered_map/
+template<class Key, class T, class IgnoredLess, class Allocator>
+struct ordered_map;
+
+/// @brief specialization that maintains the insertion order of object keys
+/// @sa https://json.nlohmann.me/api/ordered_json/
+using ordered_json = basic_json<nlohmann::ordered_map>;
+
+NLOHMANN_JSON_NAMESPACE_END
+
+#endif  // INCLUDE_NLOHMANN_JSON_FWD_HPP_
diff --git a/tools/amalgamate/config.json b/tools/amalgamate/config_json.json
similarity index 100%
rename from tools/amalgamate/config.json
rename to tools/amalgamate/config_json.json
diff --git a/tools/amalgamate/config_json_fwd.json b/tools/amalgamate/config_json_fwd.json
new file mode 100644
index 000000000..695929c15
--- /dev/null
+++ b/tools/amalgamate/config_json_fwd.json
@@ -0,0 +1,8 @@
+{
+	"project": "JSON for Modern C++",
+	"target": "single_include/nlohmann/json_fwd.hpp",
+	"sources": [
+		"include/nlohmann/json_fwd.hpp"
+	],
+	"include_paths": ["include"]
+}