diff --git a/restapi/swagger.yaml b/restapi/swagger.yaml
index f035159fe..08cb1dcd1 100644
--- a/restapi/swagger.yaml
+++ b/restapi/swagger.yaml
@@ -562,7 +562,8 @@ paths:
         "200":
           description: "preview image file"
           schema:
-            type: "file"
+            type: "string"
+            format: "binary"
         "403":
           description: "No access"
           schema:
@@ -595,7 +596,8 @@ paths:
         "200":
           description: "content file"
           schema:
-            type: "file"
+            type: "string"
+            format: "binary"
         "403":
           description: "No access"
           schema:
@@ -634,7 +636,8 @@ paths:
         "200":
           description: "attached file"
           schema:
-            type: "file"
+            type: "string"
+            format: "binary"
         "403":
           description: "No access"
           schema:
@@ -673,7 +676,8 @@ paths:
         "200":
           description: "content file"
           schema:
-            type: "file"
+            type: "string"
+            format: "binary"
         "403":
           description: "No access"
           schema: