diff --git a/ports/mpfr/CMakeLists.txt b/ports/mpfr/CMakeLists.txt
index 3fb121b76..733e6d183 100644
--- a/ports/mpfr/CMakeLists.txt
+++ b/ports/mpfr/CMakeLists.txt
@@ -250,6 +250,7 @@ add_library(mpfr ${SRCS})
 
 # target_compile_definitions(mpfr PRIVATE HAVE_CONFIG_H)
 target_compile_definitions(mpfr PRIVATE __MPFR_WITHIN_MPFR)
+target_compile_definitions(mpfr PRIVATE MPFR_USE_INTMAX_T)
 if(BUILD_SHARED_LIBS)
     target_compile_definitions(mpfr PRIVATE __GMP_LIBGMP_DLL)
 endif()