diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 2cf649c5..2718f475 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -5,16 +5,18 @@ cmake_minimum_required(VERSION 3.11 FATAL_ERROR)
 include(FetchContent)
 
 option(SYSTEM_DOCTEST "Use system copy of doctest" OFF)
+option(FASTFLOAT_SUPPLEMENTAL_TESTS "Run supplemental tests" ON)
 
 if (NOT SYSTEM_DOCTEST)
   FetchContent_Declare(doctest
     GIT_REPOSITORY https://github.com/onqtam/doctest.git
     GIT_TAG v2.4.10)
 endif()
-FetchContent_Declare(supplemental_test_files
-  GIT_REPOSITORY https://github.com/fastfloat/supplemental_test_files.git
-  GIT_TAG origin/main)
-
+if (FASTFLOAT_SUPPLEMENTAL_TESTS)
+  FetchContent_Declare(supplemental_test_files
+    GIT_REPOSITORY https://github.com/fastfloat/supplemental_test_files.git
+    GIT_TAG origin/main)
+endif()
 
 
 # FetchContent_MakeAvailable() was only introduced in 3.14
@@ -27,15 +29,19 @@ if (NOT SYSTEM_DOCTEST)
     add_subdirectory(${doctest_SOURCE_DIR} ${doctest_BINARY_DIR})
   endif()
 endif()
-FetchContent_GetProperties(supplemental_test_files)
-if(NOT supplemental_test_files_POPULATED)
-  message(STATUS "Tests enabled. Retrieving test files.")
-  FetchContent_Populate(supplemental_test_files)
-  message(STATUS "Test files retrieved.")
-  add_subdirectory(${supplemental_test_files_SOURCE_DIR} ${supplemental_test_files_BINARY_DIR})
-endif()
+
 add_library(supplemental-data INTERFACE)
-target_compile_definitions(supplemental-data INTERFACE SUPPLEMENTAL_TEST_DATA_DIR="${supplemental_test_files_BINARY_DIR}/data")
+if (FASTFLOAT_SUPPLEMENTAL_TESTS)
+  FetchContent_GetProperties(supplemental_test_files)
+  if(NOT supplemental_test_files_POPULATED)
+    message(STATUS "Supplemental tests enabled. Retrieving test files.")
+    FetchContent_Populate(supplemental_test_files)
+    message(STATUS "Supplemental test files retrieved.")
+    add_subdirectory(${supplemental_test_files_SOURCE_DIR} ${supplemental_test_files_BINARY_DIR})
+  endif()
+  target_compile_definitions(supplemental-data INTERFACE SUPPLEMENTAL_TEST_DATA_DIR="${supplemental_test_files_BINARY_DIR}/data")
+endif()
+
 function(fast_float_add_cpp_test TEST_NAME)
     add_executable(${TEST_NAME} ${TEST_NAME}.cpp)
     if(CMAKE_CROSSCOMPILING)
@@ -67,6 +73,9 @@ if (FASTFLOAT_CONSTEXPR_TESTS)
 else()
   target_compile_features(basictest PRIVATE cxx_std_17)
 endif()
+if (FASTFLOAT_SUPPLEMENTAL_TESTS)
+  target_compile_definitions(basictest PRIVATE FASTFLOAT_SUPPLEMENTAL_TESTS)
+endif()
 
 fast_float_add_cpp_test(long_test)
 fast_float_add_cpp_test(powersoffive_hardround)
diff --git a/tests/basictest.cpp b/tests/basictest.cpp
index 3d7f753f..b1b6769b 100644
--- a/tests/basictest.cpp
+++ b/tests/basictest.cpp
@@ -246,6 +246,7 @@ TEST_CASE("parse_negative_zero") {
   CHECK(float64_parsed == 0x8000'0000'0000'0000);
 }
 
+#if FASTFLOAT_SUPPLEMENTAL_TESTS
 // C++ 17 because it is otherwise annoying to browse all files in a directory.
 // We also only run these tests on little endian systems.
 #if (FASTFLOAT_CPLUSPLUS >= 201703L) && (FASTFLOAT_IS_BIG_ENDIAN == 0) && !defined(FASTFLOAT_ODDPLATFORM)
@@ -336,6 +337,7 @@ TEST_CASE("supplemental") {
     }
 }
 #endif
+#endif
 
 TEST_CASE("leading_zeroes") {
   constexpr const uint64_t bit = 1;