diff --git a/src/mongoc/mongoc-gridfs-file.c b/src/mongoc/mongoc-gridfs-file.c
index 5beb610..7e74ff7 100644
--- a/src/mongoc/mongoc-gridfs-file.c
+++ b/src/mongoc/mongoc-gridfs-file.c
@@ -734,7 +734,7 @@ _mongoc_gridfs_file_refresh_page (mongoc_gridfs_file_t *file)
    bson_t query;
    bson_t child;
    bson_t opts;
-   const bson_t *chunk;
+   const bson_t *chunk = 0;
    const char *key;
    bson_iter_t iter;
    int64_t existing_chunks;
diff --git a/src/mongoc/mongoc-handshake.c b/src/mongoc/mongoc-handshake.c
index 4e181bd..b274fc1 100644
--- a/src/mongoc/mongoc-handshake.c
+++ b/src/mongoc/mongoc-handshake.c
@@ -195,7 +195,8 @@ _get_os_version (void)
    char *ret = bson_malloc (HANDSHAKE_OS_VERSION_MAX);
    bool found = false;
 
-#ifdef _WIN32
+#if defined (WINAPI_FAMILY_PARTITION) && !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP | WINAPI_PARTITION_SYSTEM)
+#elif defined (_WIN32)
    OSVERSIONINFO osvi;
    ZeroMemory (&osvi, sizeof (OSVERSIONINFO));
    osvi.dwOSVersionInfoSize = sizeof (OSVERSIONINFO);
diff --git a/src/mongoc/mongoc-util.c b/src/mongoc/mongoc-util.c
index 6dbb26d..7f33780 100644
--- a/src/mongoc/mongoc-util.c
+++ b/src/mongoc/mongoc-util.c
@@ -46,7 +46,11 @@ _mongoc_hex_md5 (const char *input)
 void
 _mongoc_usleep (int64_t usec)
 {
-#ifdef _WIN32
+#if defined (WINAPI_FAMILY_PARTITION) && !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP | WINAPI_PARTITION_SYSTEM)
+   if (usec / 1000 > MAXDWORD || usec < 0)
+      __fastfail(-1);
+   Sleep((DWORD)(usec / 1000));
+#elif defined(_WIN32)
    LARGE_INTEGER ft;
    HANDLE timer;