diff --git a/specification/storage/data-plane/Microsoft.BlobStorage/preview/2019-12-12/blob.json b/specification/storage/data-plane/Microsoft.BlobStorage/preview/2019-12-12/blob.json
index 299115f3272e..4ec4e2e6feaf 100644
--- a/specification/storage/data-plane/Microsoft.BlobStorage/preview/2019-12-12/blob.json
+++ b/specification/storage/data-plane/Microsoft.BlobStorage/preview/2019-12-12/blob.json
@@ -9885,7 +9885,8 @@
         },
         "Size": {
           "description": "The block size in bytes.",
-          "type": "integer"
+          "type": "integer",
+          "format": "int64"
         }
       }
     },
diff --git a/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-02-10/blob.json b/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-02-10/blob.json
index da3c87709516..ab435ac4199d 100644
--- a/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-02-10/blob.json
+++ b/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-02-10/blob.json
@@ -9908,7 +9908,8 @@
         },
         "Size": {
           "description": "The block size in bytes.",
-          "type": "integer"
+          "type": "integer",
+          "format": "int64"
         }
       }
     },
diff --git a/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-04-08/blob.json b/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-04-08/blob.json
index 640ddd6fb148..ee9da931eb8b 100644
--- a/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-04-08/blob.json
+++ b/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-04-08/blob.json
@@ -10290,7 +10290,8 @@
         },
         "Size": {
           "description": "The block size in bytes.",
-          "type": "integer"
+          "type": "integer",
+          "format": "int64"
         }
       }
     },
diff --git a/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-06-12/blob.json b/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-06-12/blob.json
index a65e7acfdeda..f7b8b7bdf5c9 100644
--- a/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-06-12/blob.json
+++ b/specification/storage/data-plane/Microsoft.BlobStorage/preview/2020-06-12/blob.json
@@ -10290,7 +10290,8 @@
         },
         "Size": {
           "description": "The block size in bytes.",
-          "type": "integer"
+          "type": "integer",
+          "format": "int64"
         }
       }
     },