diff --git a/ext/ffi_c/Buffer.c b/ext/ffi_c/Buffer.c
index faf4834d0..6863dda07 100644
--- a/ext/ffi_c/Buffer.c
+++ b/ext/ffi_c/Buffer.c
@@ -114,7 +114,7 @@ buffer_initialize(int argc, VALUE* argv, VALUE self)
         }
 
         /* ensure the memory is aligned on at least a 8 byte boundary */
-        p->memory.address = (void *) (((uintptr_t) p->data.storage + 0x7) & (uintptr_t) ~0x7UL);
+        p->memory.address = (void *) (((uintptr_t) p->data.storage + 0x7) & (uintptr_t) ~0x7ULL);
     
         if (p->memory.size > 0 && (nargs < 3 || RTEST(rbClear))) {
             memset(p->memory.address, 0, p->memory.size);
@@ -154,7 +154,7 @@ buffer_initialize_copy(VALUE self, VALUE other)
         return Qnil;
     }
     
-    dst->memory.address = (void *) (((uintptr_t) dst->data.storage + 0x7) & (uintptr_t) ~0x7UL);
+    dst->memory.address = (void *) (((uintptr_t) dst->data.storage + 0x7) & (uintptr_t) ~0x7ULL);
     dst->memory.size = src->size;
     dst->memory.typeSize = src->typeSize;
     
diff --git a/ext/ffi_c/MemoryPointer.c b/ext/ffi_c/MemoryPointer.c
index 0d91c35b7..9dc59bb57 100644
--- a/ext/ffi_c/MemoryPointer.c
+++ b/ext/ffi_c/MemoryPointer.c
@@ -112,7 +112,7 @@ memptr_malloc(VALUE self, long size, long count, bool clear)
     p->memory.typeSize = (int) size;
     p->memory.size = msize;
     /* ensure the memory is aligned on at least a 8 byte boundary */
-    p->memory.address = (char *) (((uintptr_t) p->storage + 0x7) & (uintptr_t) ~0x7UL);;
+    p->memory.address = (char *) (((uintptr_t) p->storage + 0x7) & (uintptr_t) ~0x7ULL);
     p->allocated = true;
 
     if (clear && p->memory.size > 0) {
diff --git a/ext/ffi_c/MethodHandle.c b/ext/ffi_c/MethodHandle.c
index b266f995e..4dc85fbff 100644
--- a/ext/ffi_c/MethodHandle.c
+++ b/ext/ffi_c/MethodHandle.c
@@ -128,11 +128,7 @@ rbffi_function_anyargs rbffi_MethodHandle_CodeAddress(MethodHandle* handle)
 #ifndef CUSTOM_TRAMPOLINE
 static void attached_method_invoke(ffi_cif* cif, void* retval, METHOD_PARAMS parameters, void* user_data);
 
-static ffi_type* methodHandleParamTypes[] = {
-    &ffi_type_sint,
-    &ffi_type_pointer,
-    &ffi_type_ulong,
-};
+static ffi_type* methodHandleParamTypes[3];
 
 static ffi_cif mh_cif;
 
@@ -342,6 +338,10 @@ rbffi_MethodHandle_Init(VALUE module)
         rb_raise(rb_eFatal, "Could not locate offsets in trampoline code");
     }
 #else
+    methodHandleParamTypes[0] = &ffi_type_sint;
+    methodHandleParamTypes[1] = &ffi_type_pointer;
+    methodHandleParamTypes[2] = &ffi_type_ulong;
+
     ffiStatus = ffi_prep_cif(&mh_cif, FFI_DEFAULT_ABI, 3, &ffi_type_ulong,
             methodHandleParamTypes);
     if (ffiStatus != FFI_OK) {
diff --git a/ext/ffi_c/Pointer.c b/ext/ffi_c/Pointer.c
index 1eee790db..e5f24a4dc 100644
--- a/ext/ffi_c/Pointer.c
+++ b/ext/ffi_c/Pointer.c
@@ -183,7 +183,7 @@ ptr_initialize_copy(VALUE self, VALUE other)
     
     dst->allocated = true;
     dst->autorelease = true;
-    dst->memory.address = (void *) (((uintptr_t) dst->storage + 0x7) & (uintptr_t) ~0x7UL);
+    dst->memory.address = (void *) (((uintptr_t) dst->storage + 0x7) & (uintptr_t) ~0x7ULL);
     dst->memory.size = src->size;
     dst->memory.typeSize = src->typeSize;
     
diff --git a/ext/ffi_c/compat.h b/ext/ffi_c/compat.h
index a4dfc0851..3f7bbaed1 100644
--- a/ext/ffi_c/compat.h
+++ b/ext/ffi_c/compat.h
@@ -64,6 +64,10 @@
 #  define unlikely(x) (x)
 #endif
 
+#ifdef _MSC_VER
+#define ffi_type_longdouble ffi_type_double
+#endif
+
 #ifndef MAX
 #  define MAX(a, b) ((a) < (b) ? (b) : (a))
 #endif
diff --git a/ext/ffi_c/extconf.rb b/ext/ffi_c/extconf.rb
index 9bdb807a6..2e964c2e3 100644
--- a/ext/ffi_c/extconf.rb
+++ b/ext/ffi_c/extconf.rb
@@ -15,7 +15,13 @@ def system_libffi_usable?
 
     # Ensure we can link to ffi_call
     libffi_ok &&= have_library("ffi", "ffi_call", [ "ffi.h" ]) ||
-                  have_library("libffi", "ffi_call", [ "ffi.h" ])
+                  have_library("libffi", "ffi_call", [ "ffi.h" ]) ||
+                  have_library("libffi-8", "ffi_call", [ "ffi.h" ])
+
+    if RbConfig::CONFIG['host_os'] =~ /mswin/
+      have_library('libffi_convenience')
+      have_library('shlwapi')
+    end
 
     # And we need a libffi version recent enough to provide ffi_closure_alloc
     libffi_ok &&= have_func("ffi_closure_alloc")
@@ -39,7 +45,6 @@ def system_libffi_usable?
     abort "system libffi is not usable" unless system_libffi_usable?
   end
 
-  have_header('shlwapi.h')
   have_func('rb_thread_call_without_gvl') || abort("Ruby C-API function `rb_thread_call_without_gvl` is missing")
   have_func('ruby_native_thread_p')
   if RUBY_VERSION >= "2.3.0"
@@ -56,13 +61,10 @@ def system_libffi_usable?
   end
 
   $defs << "-DHAVE_EXTCONF_H" if $defs.empty? # needed so create_header works
-  $defs << "-DFFI_BUILDING" if RbConfig::CONFIG['host_os'] =~ /mswin/ # for compatibility with newer libffi
 
   create_header
-
-  $LOCAL_LIBS << " ./libffi/.libs/libffi_convenience.lib" if !system_libffi && RbConfig::CONFIG['host_os'] =~ /mswin/
-
   create_makefile("ffi_c")
+
   unless system_libffi
     File.open("Makefile", "a") do |mf|
       mf.puts "LIBFFI_HOST=--host=#{RbConfig::CONFIG['host_alias']}" if RbConfig::CONFIG.has_key?("host_alias")
diff --git a/lib/ffi/platform.rb b/lib/ffi/platform.rb
index 3e0fc6059..959a72cff 100644
--- a/lib/ffi/platform.rb
+++ b/lib/ffi/platform.rb
@@ -61,7 +61,7 @@ module Platform
     CPU = RbConfig::CONFIG['host_cpu']
 
     ARCH = case CPU.downcase
-    when /amd64|x86_64/
+    when /amd64|x86_64|x64/
       "x86_64"
     when /i?86|x86|i86pc/
       "i386"
@@ -129,7 +129,7 @@ def self.is_os(os)
     end
 
     LIBC = if IS_WINDOWS
-      RbConfig::CONFIG['RUBY_SO_NAME'].split('-')[-2] + '.dll'
+      "ucrtbase.dll"
     elsif IS_GNU
       GNU_LIBC
     elsif OS == 'cygwin'