diff --git a/CMakeLists.txt b/CMakeLists.txt
index c4dbca0..4694e30 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -44,14 +44,17 @@ endif()
 include(CheckFunctionExists)
 include(CheckSymbolExists)
 file(WRITE "libndt.hpp" "// AUTOGENERATED BY CMake! DON'T EDIT!\n\n")
-file(READ "sys.hpp" MK_AMALGAMATE_1172_0)
+file(READ "preamble.hpp" MK_AMALGAMATE_1172_0)
 file(APPEND "libndt.hpp" "${MK_AMALGAMATE_1172_0}")
 file(APPEND "libndt.hpp" "\n\n")
-file(READ "api.hpp" MK_AMALGAMATE_1172_1)
+file(READ "sys.hpp" MK_AMALGAMATE_1172_1)
 file(APPEND "libndt.hpp" "${MK_AMALGAMATE_1172_1}")
 file(APPEND "libndt.hpp" "\n\n")
-file(READ "impl.hpp" MK_AMALGAMATE_1172_2)
+file(READ "api.hpp" MK_AMALGAMATE_1172_2)
 file(APPEND "libndt.hpp" "${MK_AMALGAMATE_1172_2}")
+file(APPEND "libndt.hpp" "\n\n")
+file(READ "impl.hpp" MK_AMALGAMATE_1172_3)
+file(APPEND "libndt.hpp" "${MK_AMALGAMATE_1172_3}")
 check_function_exists(strtonum LIBNDT_HAVE_STRTONUM)
 if(${LIBNDT_HAVE_STRTONUM})
   add_definitions(-DLIBNDT_HAVE_STRTONUM)
@@ -72,9 +75,9 @@ endif()
 message(STATUS "mkdirAll: ${CMAKE_BINARY_DIR}/.mkbuild/include")
 execute_process(COMMAND
   ${CMAKE_COMMAND} -E make_directory "${CMAKE_BINARY_DIR}/.mkbuild/include"
-  RESULT_VARIABLE FAILURE_2218)
-if("${FAILURE_2218}")
-  message(FATAL_ERROR "${FAILURE_2218}")
+  RESULT_VARIABLE FAILURE_2350)
+if("${FAILURE_2350}")
+  message(FATAL_ERROR "${FAILURE_2350}")
 endif()
 message(STATUS "download: https://raw.githubusercontent.com/adishavit/argh/v1.3.1/argh.h")
 file(DOWNLOAD https://raw.githubusercontent.com/adishavit/argh/v1.3.1/argh.h
@@ -82,8 +85,8 @@ file(DOWNLOAD https://raw.githubusercontent.com/adishavit/argh/v1.3.1/argh.h
   EXPECTED_HASH SHA256=ddb7dfc18dcf90149735b76fb2cff101067453a1df1943a6911233cb7085980c
   TLS_VERIFY ON)
 LIST(APPEND CMAKE_REQUIRED_INCLUDES "${CMAKE_BINARY_DIR}/.mkbuild/include")
-CHECK_INCLUDE_FILE_CXX("argh.h" MK_HAVE_HEADER_2718)
-if(NOT ("${MK_HAVE_HEADER_2718}"))
+CHECK_INCLUDE_FILE_CXX("argh.h" MK_HAVE_HEADER_2850)
+if(NOT ("${MK_HAVE_HEADER_2850}"))
   message(FATAL_ERROR "cannot find: argh.h")
 endif()
 
@@ -94,9 +97,9 @@ endif()
 message(STATUS "mkdirAll: ${CMAKE_BINARY_DIR}/.mkbuild/include")
 execute_process(COMMAND
   ${CMAKE_COMMAND} -E make_directory "${CMAKE_BINARY_DIR}/.mkbuild/include"
-  RESULT_VARIABLE FAILURE_3042)
-if("${FAILURE_3042}")
-  message(FATAL_ERROR "${FAILURE_3042}")
+  RESULT_VARIABLE FAILURE_3174)
+if("${FAILURE_3174}")
+  message(FATAL_ERROR "${FAILURE_3174}")
 endif()
 message(STATUS "download: https://github.com/catchorg/Catch2/releases/download/v2.8.0/catch.hpp")
 file(DOWNLOAD https://github.com/catchorg/Catch2/releases/download/v2.8.0/catch.hpp
@@ -104,8 +107,8 @@ file(DOWNLOAD https://github.com/catchorg/Catch2/releases/download/v2.8.0/catch.
   EXPECTED_HASH SHA256=2791047e459b981a1035f4ee16a2ad031f5bfb4ba66487ad4d3fc816c8946f61
   TLS_VERIFY ON)
 LIST(APPEND CMAKE_REQUIRED_INCLUDES "${CMAKE_BINARY_DIR}/.mkbuild/include")
-CHECK_INCLUDE_FILE_CXX("catch.hpp" MK_HAVE_HEADER_3559)
-if(NOT ("${MK_HAVE_HEADER_3559}"))
+CHECK_INCLUDE_FILE_CXX("catch.hpp" MK_HAVE_HEADER_3691)
+if(NOT ("${MK_HAVE_HEADER_3691}"))
   message(FATAL_ERROR "cannot find: catch.hpp")
 endif()
 
@@ -118,9 +121,9 @@ if(("${WIN32}"))
   message(STATUS "mkdirAll: ${CMAKE_BINARY_DIR}/.mkbuild/download")
   execute_process(COMMAND
     ${CMAKE_COMMAND} -E make_directory "${CMAKE_BINARY_DIR}/.mkbuild/download"
-    RESULT_VARIABLE FAILURE_3940)
-  if("${FAILURE_3940}")
-    message(FATAL_ERROR "${FAILURE_3940}")
+    RESULT_VARIABLE FAILURE_4072)
+  if("${FAILURE_4072}")
+    message(FATAL_ERROR "${FAILURE_4072}")
   endif()
   message(STATUS "download: https://github.com/measurement-kit/prebuilt/releases/download//testing/windows-curl-7.61.1-1.tar.gz")
   file(DOWNLOAD https://github.com/measurement-kit/prebuilt/releases/download//testing/windows-curl-7.61.1-1.tar.gz
@@ -131,28 +134,28 @@ if(("${WIN32}"))
   execute_process(COMMAND
     ${CMAKE_COMMAND} -E tar xf "${CMAKE_BINARY_DIR}/.mkbuild/download/windows-curl-7.61.1-1.tar.gz"
     WORKING_DIRECTORY "${CMAKE_BINARY_DIR}/.mkbuild/download"
-    RESULT_VARIABLE FAILURE_4763)
-  if("${FAILURE_4763}")
-    message(FATAL_ERROR "${FAILURE_4763}")
+    RESULT_VARIABLE FAILURE_4895)
+  if("${FAILURE_4895}")
+    message(FATAL_ERROR "${FAILURE_4895}")
   endif()
   LIST(APPEND CMAKE_REQUIRED_INCLUDES "${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/curl/7.61.1-1/${MK_WIN32_ARCH}/include")
-  CHECK_INCLUDE_FILE_CXX("curl/curl.h" MK_HAVE_HEADER_5008)
-  if(NOT ("${MK_HAVE_HEADER_5008}"))
+  CHECK_INCLUDE_FILE_CXX("curl/curl.h" MK_HAVE_HEADER_5140)
+  if(NOT ("${MK_HAVE_HEADER_5140}"))
     message(FATAL_ERROR "cannot find: curl/curl.h")
   endif()
-  CHECK_LIBRARY_EXISTS("${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/curl/7.61.1-1/${MK_WIN32_ARCH}/lib/libcurl.lib" "curl_easy_init" "" MK_HAVE_LIB_5167)
-  if(NOT ("${MK_HAVE_LIB_5167}"))
+  CHECK_LIBRARY_EXISTS("${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/curl/7.61.1-1/${MK_WIN32_ARCH}/lib/libcurl.lib" "curl_easy_init" "" MK_HAVE_LIB_5299)
+  if(NOT ("${MK_HAVE_LIB_5299}"))
     message(FATAL_ERROR "cannot find: ${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/curl/7.61.1-1/${MK_WIN32_ARCH}/lib/libcurl.lib")
   endif()
   LIST(APPEND CMAKE_REQUIRED_LIBRARIES "${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/curl/7.61.1-1/${MK_WIN32_ARCH}/lib/libcurl.lib")
   LIST(APPEND CMAKE_REQUIRED_DEFINITIONS -DCURL_STATICLIB)
 else()
-  CHECK_INCLUDE_FILE_CXX("curl/curl.h" MK_HAVE_HEADER_5725)
-  if(NOT ("${MK_HAVE_HEADER_5725}"))
+  CHECK_INCLUDE_FILE_CXX("curl/curl.h" MK_HAVE_HEADER_5857)
+  if(NOT ("${MK_HAVE_HEADER_5857}"))
     message(FATAL_ERROR "cannot find: curl/curl.h")
   endif()
-  CHECK_LIBRARY_EXISTS("curl" "curl_easy_init" "" MK_HAVE_LIB_5884)
-  if(NOT ("${MK_HAVE_LIB_5884}"))
+  CHECK_LIBRARY_EXISTS("curl" "curl_easy_init" "" MK_HAVE_LIB_6016)
+  if(NOT ("${MK_HAVE_LIB_6016}"))
     message(FATAL_ERROR "cannot find: curl")
   endif()
   LIST(APPEND CMAKE_REQUIRED_LIBRARIES "curl")
@@ -165,9 +168,9 @@ endif()
 message(STATUS "mkdirAll: ${CMAKE_BINARY_DIR}/.mkbuild/download")
 execute_process(COMMAND
   ${CMAKE_COMMAND} -E make_directory "${CMAKE_BINARY_DIR}/.mkbuild/download"
-  RESULT_VARIABLE FAILURE_6308)
-if("${FAILURE_6308}")
-  message(FATAL_ERROR "${FAILURE_6308}")
+  RESULT_VARIABLE FAILURE_6440)
+if("${FAILURE_6440}")
+  message(FATAL_ERROR "${FAILURE_6440}")
 endif()
 message(STATUS "download: https://github.com/measurement-kit/generic-assets/releases/download/20190520205742/generic-assets-20190520205742.tar.gz")
 file(DOWNLOAD https://github.com/measurement-kit/generic-assets/releases/download/20190520205742/generic-assets-20190520205742.tar.gz
@@ -178,9 +181,9 @@ message(STATUS "Extract: ${CMAKE_BINARY_DIR}/.mkbuild/download/generic-assets-20
 execute_process(COMMAND
   ${CMAKE_COMMAND} -E tar xf "${CMAKE_BINARY_DIR}/.mkbuild/download/generic-assets-20190520205742.tar.gz"
   WORKING_DIRECTORY "${CMAKE_BINARY_DIR}/.mkbuild/download"
-  RESULT_VARIABLE FAILURE_7169)
-if("${FAILURE_7169}")
-  message(FATAL_ERROR "${FAILURE_7169}")
+  RESULT_VARIABLE FAILURE_7301)
+if("${FAILURE_7301}")
+  message(FATAL_ERROR "${FAILURE_7301}")
 endif()
 
 #
@@ -190,9 +193,9 @@ endif()
 message(STATUS "mkdirAll: ${CMAKE_BINARY_DIR}/.mkbuild/include")
 execute_process(COMMAND
   ${CMAKE_COMMAND} -E make_directory "${CMAKE_BINARY_DIR}/.mkbuild/include"
-  RESULT_VARIABLE FAILURE_7454)
-if("${FAILURE_7454}")
-  message(FATAL_ERROR "${FAILURE_7454}")
+  RESULT_VARIABLE FAILURE_7586)
+if("${FAILURE_7586}")
+  message(FATAL_ERROR "${FAILURE_7586}")
 endif()
 message(STATUS "download: https://raw.githubusercontent.com/nlohmann/json/v3.6.1/single_include/nlohmann/json.hpp")
 file(DOWNLOAD https://raw.githubusercontent.com/nlohmann/json/v3.6.1/single_include/nlohmann/json.hpp
@@ -200,8 +203,8 @@ file(DOWNLOAD https://raw.githubusercontent.com/nlohmann/json/v3.6.1/single_incl
   EXPECTED_HASH SHA256=d2eeb25d2e95bffeb08ebb7704cdffd2e8fca7113eba9a0b38d60a5c391ea09a
   TLS_VERIFY ON)
 LIST(APPEND CMAKE_REQUIRED_INCLUDES "${CMAKE_BINARY_DIR}/.mkbuild/include")
-CHECK_INCLUDE_FILE_CXX("json.hpp" MK_HAVE_HEADER_8006)
-if(NOT ("${MK_HAVE_HEADER_8006}"))
+CHECK_INCLUDE_FILE_CXX("json.hpp" MK_HAVE_HEADER_8138)
+if(NOT ("${MK_HAVE_HEADER_8138}"))
   message(FATAL_ERROR "cannot find: json.hpp")
 endif()
 
@@ -214,9 +217,9 @@ if(("${WIN32}"))
   message(STATUS "mkdirAll: ${CMAKE_BINARY_DIR}/.mkbuild/download")
   execute_process(COMMAND
     ${CMAKE_COMMAND} -E make_directory "${CMAKE_BINARY_DIR}/.mkbuild/download"
-    RESULT_VARIABLE FAILURE_8388)
-  if("${FAILURE_8388}")
-    message(FATAL_ERROR "${FAILURE_8388}")
+    RESULT_VARIABLE FAILURE_8520)
+  if("${FAILURE_8520}")
+    message(FATAL_ERROR "${FAILURE_8520}")
   endif()
   message(STATUS "download: https://github.com/measurement-kit/prebuilt/releases/download//testing/windows-libressl-2.7.4-1.tar.gz")
   file(DOWNLOAD https://github.com/measurement-kit/prebuilt/releases/download//testing/windows-libressl-2.7.4-1.tar.gz
@@ -227,22 +230,22 @@ if(("${WIN32}"))
   execute_process(COMMAND
     ${CMAKE_COMMAND} -E tar xf "${CMAKE_BINARY_DIR}/.mkbuild/download/windows-libressl-2.7.4-1.tar.gz"
     WORKING_DIRECTORY "${CMAKE_BINARY_DIR}/.mkbuild/download"
-    RESULT_VARIABLE FAILURE_9226)
-  if("${FAILURE_9226}")
-    message(FATAL_ERROR "${FAILURE_9226}")
+    RESULT_VARIABLE FAILURE_9358)
+  if("${FAILURE_9358}")
+    message(FATAL_ERROR "${FAILURE_9358}")
   endif()
   LIST(APPEND CMAKE_REQUIRED_INCLUDES "${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/libressl/2.7.4-1/${MK_WIN32_ARCH}/include")
-  CHECK_INCLUDE_FILE_CXX("openssl/rsa.h" MK_HAVE_HEADER_9474)
-  if(NOT ("${MK_HAVE_HEADER_9474}"))
+  CHECK_INCLUDE_FILE_CXX("openssl/rsa.h" MK_HAVE_HEADER_9606)
+  if(NOT ("${MK_HAVE_HEADER_9606}"))
     message(FATAL_ERROR "cannot find: openssl/rsa.h")
   endif()
-  CHECK_LIBRARY_EXISTS("${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/libressl/2.7.4-1/${MK_WIN32_ARCH}/lib/crypto.lib" "RSA_new" "" MK_HAVE_LIB_9637)
-  if(NOT ("${MK_HAVE_LIB_9637}"))
+  CHECK_LIBRARY_EXISTS("${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/libressl/2.7.4-1/${MK_WIN32_ARCH}/lib/crypto.lib" "RSA_new" "" MK_HAVE_LIB_9769)
+  if(NOT ("${MK_HAVE_LIB_9769}"))
     message(FATAL_ERROR "cannot find: ${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/libressl/2.7.4-1/${MK_WIN32_ARCH}/lib/crypto.lib")
   endif()
   LIST(APPEND CMAKE_REQUIRED_LIBRARIES "${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/libressl/2.7.4-1/${MK_WIN32_ARCH}/lib/crypto.lib")
-  CHECK_LIBRARY_EXISTS("${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/libressl/2.7.4-1/${MK_WIN32_ARCH}/lib/ssl.lib" "SSL_new" "" MK_HAVE_LIB_10128)
-  if(NOT ("${MK_HAVE_LIB_10128}"))
+  CHECK_LIBRARY_EXISTS("${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/libressl/2.7.4-1/${MK_WIN32_ARCH}/lib/ssl.lib" "SSL_new" "" MK_HAVE_LIB_10260)
+  if(NOT ("${MK_HAVE_LIB_10260}"))
     message(FATAL_ERROR "cannot find: ${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/libressl/2.7.4-1/${MK_WIN32_ARCH}/lib/ssl.lib")
   endif()
   LIST(APPEND CMAKE_REQUIRED_LIBRARIES "${CMAKE_BINARY_DIR}/.mkbuild/download/MK_DIST/windows/libressl/2.7.4-1/${MK_WIN32_ARCH}/lib/ssl.lib")
@@ -256,21 +259,21 @@ else()
         set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -L/usr/local/opt/openssl@1.1/lib")
     endif()
   endif()
-  CHECK_INCLUDE_FILE_CXX("openssl/rsa.h" MK_HAVE_HEADER_11075)
-  if(NOT ("${MK_HAVE_HEADER_11075}"))
+  CHECK_INCLUDE_FILE_CXX("openssl/rsa.h" MK_HAVE_HEADER_11207)
+  if(NOT ("${MK_HAVE_HEADER_11207}"))
     message(FATAL_ERROR "cannot find: openssl/rsa.h")
   endif()
-  CHECK_LIBRARY_EXISTS("crypto" "RSA_new" "" MK_HAVE_LIB_11240)
-  if(NOT ("${MK_HAVE_LIB_11240}"))
+  CHECK_LIBRARY_EXISTS("crypto" "RSA_new" "" MK_HAVE_LIB_11372)
+  if(NOT ("${MK_HAVE_LIB_11372}"))
     message(FATAL_ERROR "cannot find: crypto")
   endif()
   LIST(APPEND CMAKE_REQUIRED_LIBRARIES "crypto")
-  CHECK_INCLUDE_FILE_CXX("openssl/ssl.h" MK_HAVE_HEADER_11445)
-  if(NOT ("${MK_HAVE_HEADER_11445}"))
+  CHECK_INCLUDE_FILE_CXX("openssl/ssl.h" MK_HAVE_HEADER_11577)
+  if(NOT ("${MK_HAVE_HEADER_11577}"))
     message(FATAL_ERROR "cannot find: openssl/ssl.h")
   endif()
-  CHECK_LIBRARY_EXISTS("ssl" "SSL_read" "" MK_HAVE_LIB_11610)
-  if(NOT ("${MK_HAVE_LIB_11610}"))
+  CHECK_LIBRARY_EXISTS("ssl" "SSL_read" "" MK_HAVE_LIB_11742)
+  if(NOT ("${MK_HAVE_LIB_11742}"))
     message(FATAL_ERROR "cannot find: ssl")
   endif()
   LIST(APPEND CMAKE_REQUIRED_LIBRARIES "ssl")
@@ -351,20 +354,33 @@ include_directories(${CMAKE_REQUIRED_INCLUDES})
 
 add_executable(
   libndt-client
-  libndt-client.cpp
+  libndt-client.cpp api.hpp impl.hpp sys.hpp
 )
 target_link_libraries(
   libndt-client
   ${CMAKE_REQUIRED_LIBRARIES}
 )
 
+#
+# libndt-standalne-builds
+#
+
+add_executable(
+  libndt-standalne-builds
+  libndt-standalone-builds.cpp libndt.hpp
+)
+target_link_libraries(
+  libndt-standalne-builds
+  ${CMAKE_REQUIRED_LIBRARIES}
+)
+
 #
 # sys_test
 #
 
 add_executable(
   sys_test
-  sys_test.cpp
+  sys_test.cpp api.hpp impl.hpp sys.hpp
 )
 target_link_libraries(
   sys_test
@@ -377,7 +393,7 @@ target_link_libraries(
 
 add_executable(
   tests-curl
-  curlx_test.cpp
+  curlx_test.cpp api.hpp impl.hpp sys.hpp
 )
 target_link_libraries(
   tests-curl
@@ -390,7 +406,7 @@ target_link_libraries(
 
 add_executable(
   tests-libndt
-  libndt_test.cpp
+  libndt_test.cpp api.hpp impl.hpp sys.hpp
 )
 target_link_libraries(
   tests-libndt
diff --git a/MKBuild.yaml b/MKBuild.yaml
index fa2e2ec..705a7d2 100644
--- a/MKBuild.yaml
+++ b/MKBuild.yaml
@@ -5,6 +5,7 @@ docker_tc_disabled: true
 
 amalgamate:
   libndt.hpp:
+  - preamble.hpp
   - sys.hpp
   - api.hpp
   - impl.hpp
@@ -32,13 +33,15 @@ dependencies:
 targets:
   executables:
     libndt-client:
-      compile: [libndt-client.cpp]
+      compile: [libndt-client.cpp api.hpp impl.hpp sys.hpp]
+    libndt-standalne-builds:
+      compile: [libndt-standalone-builds.cpp libndt.hpp]
     sys_test:
-      compile: [sys_test.cpp]
+      compile: [sys_test.cpp api.hpp impl.hpp sys.hpp]
     tests-curl:
-      compile: [curlx_test.cpp]
+      compile: [curlx_test.cpp api.hpp impl.hpp sys.hpp]
     tests-libndt:
-      compile: [libndt_test.cpp]
+      compile: [libndt_test.cpp api.hpp impl.hpp sys.hpp]
 
 tests:
   curl_unit_tests:
diff --git a/curlx_test.cpp b/curlx_test.cpp
index c8d690c..530c4b8 100644
--- a/curlx_test.cpp
+++ b/curlx_test.cpp
@@ -3,7 +3,8 @@
 // and LICENSE for more information on the copying conditions.
 
 #include "json.hpp"
-#include "libndt.hpp"
+
+#include "impl.hpp" // not standalone
 
 #define CATCH_CONFIG_MAIN
 #include "catch.hpp"
diff --git a/impl.hpp b/impl.hpp
index b290f8e..b1ab827 100644
--- a/impl.hpp
+++ b/impl.hpp
@@ -1,6 +1,11 @@
 #ifndef MEASUREMENT_KIT_LIBNDT_IMPL_HPP
 #define MEASUREMENT_KIT_LIBNDT_IMPL_HPP
 
+#ifndef LIBNDT_STANDALONE
+#include "sys.hpp"
+#include "api.hpp"
+#endif // !LIBNDT_STANDALONE
+
 // Implementation section
 // ``````````````````````
 // This is a single header library. In some use cases you may want to split
diff --git a/libndt-client.cpp b/libndt-client.cpp
index 91bff60..ad22d80 100644
--- a/libndt-client.cpp
+++ b/libndt-client.cpp
@@ -3,7 +3,8 @@
 // and LICENSE for more information on the copying conditions.
 
 #include "json.hpp"
-#include "libndt.hpp"
+
+#include "impl.hpp" // not standalone
 
 #include <stdlib.h>
 
diff --git a/libndt-standalone-builds.cpp b/libndt-standalone-builds.cpp
new file mode 100644
index 0000000..7f830fe
--- /dev/null
+++ b/libndt-standalone-builds.cpp
@@ -0,0 +1,12 @@
+// The purpose of this file is to make sure the standalone
+// header is building. We're now using the individual headers
+// elsewhere, and specifically "impl.hpp", such that it's
+// significantly simpler to do development.
+#include "json.hpp"
+#include "libndt.hpp"
+int main() {
+  measurement_kit::libndt::Client client{
+    measurement_kit::libndt::Settings{}
+  };
+  client.run();
+}
diff --git a/libndt_test.cpp b/libndt_test.cpp
index 5ec0710..050c16f 100644
--- a/libndt_test.cpp
+++ b/libndt_test.cpp
@@ -3,7 +3,8 @@
 // and LICENSE for more information on the copying conditions.
 
 #include "json.hpp"
-#include "libndt.hpp"
+
+#include "impl.hpp" // not standalone
 
 #ifndef _WIN32
 #include <arpa/inet.h>
diff --git a/preamble.hpp b/preamble.hpp
new file mode 100644
index 0000000..d095158
--- /dev/null
+++ b/preamble.hpp
@@ -0,0 +1,3 @@
+#ifndef LIBNDT_STANDALONE
+#define LIBNDT_STANDALONE 1
+#endif