diff --git a/ext/json/ext/generator/extconf.rb b/ext/json/ext/generator/extconf.rb
index aaf02c77d..fb9afd07f 100644
--- a/ext/json/ext/generator/extconf.rb
+++ b/ext/json/ext/generator/extconf.rb
@@ -9,7 +9,7 @@
   $defs << "-DJSON_DEBUG" if ENV["JSON_DEBUG"]
 
   if enable_config('generator-use-simd', default=!ENV["JSON_DISABLE_SIMD"])
-    require_relative "../simd/conf.rb"
+    load __dir__ + "/../simd/conf.rb"
   end
 
   create_makefile 'json/ext/generator'
diff --git a/ext/json/ext/parser/extconf.rb b/ext/json/ext/parser/extconf.rb
index 0b62fd613..84049a7fe 100644
--- a/ext/json/ext/parser/extconf.rb
+++ b/ext/json/ext/parser/extconf.rb
@@ -9,7 +9,7 @@
 append_cflags("-std=c99")
 
 if enable_config('parser-use-simd', default=!ENV["JSON_DISABLE_SIMD"])
-  require_relative "../simd/conf.rb"
+  load __dir__ + "/../simd/conf.rb"
 end
 
 create_makefile 'json/ext/parser'
diff --git a/ext/json/ext/parser/parser.c b/ext/json/ext/parser/parser.c
index d77969482..9bf247039 100644
--- a/ext/json/ext/parser/parser.c
+++ b/ext/json/ext/parser/parser.c
@@ -908,7 +908,7 @@ static inline bool FORCE_INLINE string_scan(JSON_ParserState *state)
 {
 #ifdef HAVE_SIMD
 #if defined(HAVE_SIMD_NEON)
-    
+
     uint64_t mask = 0;
     if (string_scan_simd_neon(&state->cursor, state->end, &mask)) {
         state->cursor += trailing_zeros64(mask) >> 2;
diff --git a/ext/json/ext/simd/conf.rb b/ext/json/ext/simd/conf.rb
index 6393cf789..8e7d8ee26 100644
--- a/ext/json/ext/simd/conf.rb
+++ b/ext/json/ext/simd/conf.rb
@@ -1,25 +1,20 @@
-if RbConfig::CONFIG['host_cpu'] =~ /^(arm.*|aarch64.*)/
+case RbConfig::CONFIG['host_cpu']
+when /^(arm|aarch64)/
   # Try to compile a small program using NEON instructions
-  if have_header('arm_neon.h')
-    have_type('uint8x16_t', headers=['arm_neon.h']) && try_compile(<<~'SRC')
-      #include <arm_neon.h>
-      int main() {
-          uint8x16_t test = vdupq_n_u8(32);
-          return 0;
-      }
-    SRC
-      $defs.push("-DJSON_ENABLE_SIMD")
-  end
+  header, type, init = 'arm_neon.h', 'uint8x16_t', 'vdupq_n_u8(32)'
+when /^(x86_64|x64)/
+  header, type, init = 'x86intrin.h', '__m128i', '_mm_set1_epi8(32)'
 end
-
-if have_header('x86intrin.h') && have_type('__m128i', headers=['x86intrin.h']) && try_compile(<<~'SRC')
-  #include <x86intrin.h>
-  int main() {
-      __m128i test = _mm_set1_epi8(32);
+if header
+  have_header(header) && try_compile(<<~SRC)
+    #{cpp_include(header)}
+    int main(int argc, char **argv) {
+      #{type} test = #{init};
+      if (argc > 100000) printf("%p", &test);
       return 0;
-  }
+    }
   SRC
-    $defs.push("-DJSON_ENABLE_SIMD")
+  $defs.push("-DJSON_ENABLE_SIMD")
 end
 
 have_header('cpuid.h')