diff --git a/InnerEye/Scripts/prepare_fastmri.py b/InnerEye/Scripts/prepare_fastmri.py
index 6f6d2910..95f1594e 100644
--- a/InnerEye/Scripts/prepare_fastmri.py
+++ b/InnerEye/Scripts/prepare_fastmri.py
@@ -333,7 +333,7 @@ def extract_access_tokens(text: str) -> Dict[str, str]:
     :return:
     """
     result: Dict[str, str] = {}
-    for match in re.finditer(r'(https://fastmri-dataset.s3.amazonaws.com/)([._a-zA-Z0-9]+)(\?[a-zA-Z0-9=&%]+)', text):
+    for match in re.finditer(r'(https://fastmri-dataset\.s3\.amazonaws\.com/)([._a-zA-Z0-9]+)(\?[a-zA-Z0-9=&%]+)', text):
         file = match.group(2)
         token = match.group(3)
         if file in result: