diff --git a/Tusker/Models/CompositionAttachmentData.swift b/Tusker/Models/CompositionAttachmentData.swift
index b8f424a6..3f5fa6dc 100644
--- a/Tusker/Models/CompositionAttachmentData.swift
+++ b/Tusker/Models/CompositionAttachmentData.swift
@@ -51,7 +51,10 @@ enum CompositionAttachmentData {
     func getData(completion: @escaping (_ data: Data, _ mimeType: String) -> Void) {
         switch self {
         case let .image(image):
-            completion(image.pngData()!, "image/png")
+            // Export as JPEG instead of PNG, otherweise photos straight from the camera are too large
+            // for Mastodon in its default configuration (max of 10MB).
+            // The quality of 0.8 was chosen completely arbitrarily, it may need to be tuned in the future.
+            completion(image.jpegData(compressionQuality: 0.8)!, "image/jpeg")
         case let .asset(asset):
             if asset.mediaType == .image {
                 let options = PHImageRequestOptions()