diff --git a/CMakeLists.txt b/CMakeLists.txt
index cce4efe4..7db567c0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -32,17 +32,6 @@ else()
     add_definitions(-DSEXP_USE_DL=0)
 endif()
 
-if(CMAKE_SIZEOF_VOID_P EQUAL 8)
-    if(MSVC)
-        # On MSVC, SEXP_64_BIT is not supported for now (#438)
-        add_definitions(-DSEXP_64_BIT=0)
-    else()
-        add_definitions(-DSEXP_64_BIT=1)
-    endif()
-elseif(CMAKE_SIZEOF_VOID_P EQUAL 4)
-    add_definitions(-DSEXP_64_BIT=0)
-endif()
-
 if(HAVE_STDINT_H)
     add_definitions(-DSEXP_USE_INTTYPES=1)
 endif()
diff --git a/include/chibi/sexp.h b/include/chibi/sexp.h
index c0e83e28..1a97c683 100644
--- a/include/chibi/sexp.h
+++ b/include/chibi/sexp.h
@@ -209,10 +209,6 @@ enum sexp_types {
 #endif
 
 #ifdef _WIN32
-#if defined(_MSC_VER) && SEXP_64_BIT
-/* On SEXP_64_BIT, 128bits arithmetic is mandatory */
-#error Unsupported configuration
-#endif
 #if SEXP_64_BIT
 typedef unsigned int sexp_tag_t;
 typedef unsigned long long sexp_uint_t;