diff --git a/include/mio/detail/mmap.ipp b/include/mio/detail/mmap.ipp
index 2045cd1..be6ef92 100644
--- a/include/mio/detail/mmap.ipp
+++ b/include/mio/detail/mmap.ipp
@@ -324,7 +324,9 @@ void basic_mmap<AccessMode, ByteT>::map(const handle_type handle,
 }
 
 template<access_mode AccessMode, typename ByteT>
-void basic_mmap<AccessMode, ByteT>::sync_impl(std::error_code& error)
+template<access_mode A>
+typename std::enable_if<A == access_mode::write, void>::type
+basic_mmap<AccessMode, ByteT>::sync(std::error_code& error)
 {
     error.clear();
     if(!is_open())
diff --git a/include/mio/mmap.hpp b/include/mio/mmap.hpp
index 694d9f4..2e69e63 100644
--- a/include/mio/mmap.hpp
+++ b/include/mio/mmap.hpp
@@ -341,13 +341,9 @@ public:
     void swap(basic_mmap& other);
 
     /** Flushes the memory mapped page to disk. Errors are reported via `error`. */
-    template<
-        access_mode A = AccessMode,
-        typename = typename std::enable_if<A == access_mode::write>::type
-    > void sync(std::error_code& error)
-    {
-        sync_impl(error);
-    }
+    template<access_mode A = AccessMode>
+    typename std::enable_if<A == access_mode::write, void>::type
+    sync(std::error_code& error);
 
     /**
      * All operators compare the address of the first byte and size of the two mapped
@@ -378,15 +374,6 @@ private:
     conditional_sync();
     template<access_mode A = AccessMode>
     typename std::enable_if<A == access_mode::read, void>::type conditional_sync();
-
-    /**
-     * Due to MSVC's fragile SFINAE support (see
-     * https://github.com/mandreyel/mio/issues/300), we need to have `sync`
-     * defined inline so that `conditional_sync` sees the definition. To not
-     * clutter the API, the implementation is extracted into this non-SFINAE
-     * private member function.
-     */
-    void sync_impl(std::error_code& error);
 };
 
 template<access_mode AccessMode, typename ByteT>