diff --git a/src/handlers/attachments.ts b/src/handlers/attachments.ts
index f13942e..b7fadce 100644
--- a/src/handlers/attachments.ts
+++ b/src/handlers/attachments.ts
@@ -196,7 +196,7 @@ export async function handleGetAttachment(
     url: downloadUrl,
     fileName: attachment.fileName,
     key: attachment.key,
-    size: String(attachment.size),
+    size: Number(attachment.size) || 0,
     sizeName: attachment.sizeName,
   });
 }
@@ -332,10 +332,10 @@ function formatCipherResponse(cipher: Cipher, attachments: Attachment[]): any {
     attachments: attachments.length > 0 ? attachments.map(a => ({
       id: a.id,
       fileName: a.fileName,
-      size: String(a.size),
+      size: Number(a.size) || 0,
       sizeName: a.sizeName,
       key: a.key,
-      url: null,
+      url: `/api/ciphers/${a.cipherId}/attachment/${a.id}`,
       object: 'attachment',
     })) : null,
     key: cipher.key,
diff --git a/src/handlers/ciphers.ts b/src/handlers/ciphers.ts
index aaf3c92..3e2257b 100644
--- a/src/handlers/ciphers.ts
+++ b/src/handlers/ciphers.ts
@@ -10,10 +10,10 @@ function formatAttachments(attachments: Attachment[]): any[] | null {
   return attachments.map(a => ({
     id: a.id,
     fileName: a.fileName,
-    size: String(a.size),
+    size: Number(a.size) || 0,  // Android expects Int, not String
     sizeName: a.sizeName,
     key: a.key,
-    url: null,
+    url: `/api/ciphers/${a.cipherId}/attachment/${a.id}`,  // Android requires non-null url!
     object: 'attachment',
   }));
 }
diff --git a/src/handlers/sync.ts b/src/handlers/sync.ts
index 825c7ea..ea7236f 100644
--- a/src/handlers/sync.ts
+++ b/src/handlers/sync.ts
@@ -8,10 +8,10 @@ function formatAttachments(attachments: Attachment[]): any[] | null {
   return attachments.map(a => ({
     id: a.id,
     fileName: a.fileName,
-    size: String(a.size),
+    size: Number(a.size) || 0,  // Android expects Int, not String
     sizeName: a.sizeName,
     key: a.key,
-    url: null,
+    url: `/api/ciphers/${a.cipherId}/attachment/${a.id}`,  // Android requires non-null url!
     object: 'attachment',
   }));
 }