diff --git a/CMakeLists.txt b/CMakeLists.txt
index d819e59..e6ac7fe 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -173,15 +173,23 @@ if (CMAKE_CXX_COMPILER_TARGET)
 endif()
 CHECK_CXX_SOURCE_COMPILES("
 #include <cstdlib>
+#include <cstdint>
+#include <bit>
 int main(int argc, char **argv) {
 __fp16 a = (__fp16)(float)atof(argv[1]);
+__uint16_t u = std::bit_cast<__uint16_t>(a);
+a = std::bit_cast<__fp16>(u);
 return (float)a; }
 " TLFLOAT_COMPILER_SUPPORTS_FP16)
 
 CHECK_CXX_SOURCE_COMPILES("
 #include <cstdlib>
+#include <cstdint>
+#include <bit>
 int main(int argc, char **argv) {
 __bf16 a = (__bf16)(float)atof(argv[1]);
+__uint16_t u = std::bit_cast<__uint16_t>(a);
+a = std::bit_cast<__bf16>(u);
 return (float)a; }
 " TLFLOAT_COMPILER_SUPPORTS_BF16)
 
diff --git a/src/tester/test_exhaustive_bf16_mpfr.cpp b/src/tester/test_exhaustive_bf16_mpfr.cpp
index 6c962bf..d61b2e6 100644
--- a/src/tester/test_exhaustive_bf16_mpfr.cpp
+++ b/src/tester/test_exhaustive_bf16_mpfr.cpp
@@ -1,6 +1,13 @@
 #include <iostream>
 #include <atomic>
 #include <signal.h>
+
+#include <detect.h>
+
+#if defined(TLFLOAT_ENABLE_MPFR_WANT_FLOAT128)
+#define MPFR_WANT_FLOAT128
+#endif
+
 #include <mpfr.h>
 
 #include "suppress.hpp"