diff --git a/external/fs/fs.c b/external/fs/fs.c
index eefd2abe..20bd803b 100644
--- a/external/fs/fs.c
+++ b/external/fs/fs.c
@@ -5410,7 +5410,7 @@ static fs_result fs_serialize_directory(fs* pFS, const char* pDirectoryPath, con
             *pRunningFileOffset += fileSize;
 
             /* Add padding zeros to align the data to 8 bytes. */
-            result = fs_stream_write(pOutputStream, padding, FS_ALIGN(*pRunningFileOffset, 8) - *pRunningFileOffset, NULL);
+            result = fs_stream_write(pOutputStream, padding, (size_t)(FS_ALIGN(*pRunningFileOffset, 8) - *pRunningFileOffset), NULL);
             if (result != FS_SUCCESS) {
                 fs_string_free(&path, fs_get_allocation_callbacks(pFS));
                 return result;
@@ -5487,7 +5487,7 @@ FS_API fs_result fs_serialize(fs* pFS, const char* pDirectoryPath, int options,
         return result;
     }
 
-    result = fs_stream_write(pOutputStream, "\0\0\0\0\0\0\0\0", FS_ALIGN(initialPos, 8) - initialPos, NULL);
+    result = fs_stream_write(pOutputStream, "\0\0\0\0\0\0\0\0", (size_t)(FS_ALIGN(initialPos, 8) - initialPos), NULL);
     if (result != FS_SUCCESS) {
         fs_memory_stream_uninit(&toc);
         return result;
@@ -5532,7 +5532,7 @@ FS_API fs_result fs_serialize(fs* pFS, const char* pDirectoryPath, int options,
         fs_uint32 reserved;
 
         /* Padding to align to 8 bytes. */
-        result = fs_stream_write(pOutputStream, padding, FS_ALIGN(runningOffset, 8) - runningOffset, NULL);
+        result = fs_stream_write(pOutputStream, padding, (size_t)(FS_ALIGN(runningOffset, 8) - runningOffset), NULL);
         if (result != FS_SUCCESS) {
             return result;
         }
diff --git a/external/fs/fs.h b/external/fs/fs.h
index 3d961a67..da716042 100644
--- a/external/fs/fs.h
+++ b/external/fs/fs.h
@@ -3689,6 +3689,7 @@ FS_API void* fs_sorted_search(const void* pKey, const void* pList, size_t count,
 
 FS_API int fs_strncmp(const char* str1, const char* str2, size_t maxLen);
 FS_API int fs_strnicmp(const char* str1, const char* str2, size_t count);
+FS_API int fs_strncat_s(char* dst, size_t dstCap, const char* src, size_t count);
 /* END fs_utils.h */