diff --git a/external/fs/fs.c b/external/fs/fs.c
index ae23e53f..e3c625f1 100644
--- a/external/fs/fs.c
+++ b/external/fs/fs.c
@@ -646,6 +646,10 @@ FS_API fs_result fs_stream_read(fs_stream* pStream, void* pDst, size_t bytesToRe
     size_t bytesRead;
     fs_result result;
 
+    if (pBytesRead != NULL) {
+        *pBytesRead = 0;
+    }
+
     if (pStream == NULL) {
         return FS_INVALID_ARGS;
     }
@@ -669,6 +673,10 @@ FS_API fs_result fs_stream_write(fs_stream* pStream, const void* pSrc, size_t by
     size_t bytesWritten;
     fs_result result;
 
+    if (pBytesWritten != NULL) {
+        *pBytesWritten = 0;
+    }
+
     if (pStream == NULL) {
         return FS_INVALID_ARGS;
     }