diff --git a/include/mio/detail/mmap.ipp b/include/mio/detail/mmap.ipp
index a068891..2045cd1 100644
--- a/include/mio/detail/mmap.ipp
+++ b/include/mio/detail/mmap.ipp
@@ -324,8 +324,7 @@ void basic_mmap<AccessMode, ByteT>::map(const handle_type handle,
 }
 
 template<access_mode AccessMode, typename ByteT>
-template<access_mode, typename /*SFINAE*/>
-void basic_mmap<AccessMode, ByteT>::sync(std::error_code& error)
+void basic_mmap<AccessMode, ByteT>::sync_impl(std::error_code& error)
 {
     error.clear();
     if(!is_open())
diff --git a/include/mio/mmap.hpp b/include/mio/mmap.hpp
index 2d18cd9..694d9f4 100644
--- a/include/mio/mmap.hpp
+++ b/include/mio/mmap.hpp
@@ -344,7 +344,10 @@ public:
     template<
         access_mode A = AccessMode,
         typename = typename std::enable_if<A == access_mode::write>::type
-    > void sync(std::error_code& error);
+    > void sync(std::error_code& error)
+    {
+        sync_impl(error);
+    }
 
     /**
      * All operators compare the address of the first byte and size of the two mapped
@@ -375,6 +378,15 @@ 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>