diff --git a/icons/CMakeLists.txt b/icons/CMakeLists.txt
index ec57db4..c48586b 100644
--- a/icons/CMakeLists.txt
+++ b/icons/CMakeLists.txt
@@ -4,6 +4,14 @@
 
 # Named after the app ID, as the desktop file, the window icon and Flatpak
 # (which only exports icons prefixed with the app ID) all expect.
+# Image loaders (gdk-pixbuf, and so AppStream compose in the Flatpak build)
+# recognise an SVG by finding "<svg" in its first 256 bytes; past that the
+# file is "Unrecognized image file format" and the Flatpak build fails.
+file(READ sc-apps-io.github.toservetheking.Kareer.svg _kareer_svg_head LIMIT 256)
+if(NOT _kareer_svg_head MATCHES "<svg")
+    message(FATAL_ERROR "icons/sc-apps-io.github.toservetheking.Kareer.svg: the <svg> tag must start within the first 256 bytes; move comments inside the element.")
+endif()
+
 ecm_install_icons(ICONS
     sc-apps-io.github.toservetheking.Kareer.svg
     128-apps-io.github.toservetheking.Kareer.png
diff --git a/icons/sc-apps-io.github.toservetheking.Kareer.svg b/icons/sc-apps-io.github.toservetheking.Kareer.svg
index 34d7d7c..d8238f3 100644
--- a/icons/sc-apps-io.github.toservetheking.Kareer.svg
+++ b/icons/sc-apps-io.github.toservetheking.Kareer.svg
@@ -1,13 +1,15 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!-- SPDX-FileCopyrightText: 2026 ToServeTheKing <austin@thebennett.net> -->
 <!-- SPDX-License-Identifier: GPL-3.0-or-later -->
-<!--
-  A K for Kareer, drawn as its application pipeline: the stem is every
-  application, splitting into a success path rising to an outcome and a
-  drop-off falling away. Plain shapes and gradients only, so QtSvg (which
-  ignores filters) renders it exactly as other renderers do.
--->
 <svg width="128" height="128" viewBox="0 0 128 128" xmlns="http://www.w3.org/2000/svg">
+  <!--
+    A K for Kareer, drawn as its application pipeline: the stem is every
+    application, splitting into a success path rising to an outcome and a
+    drop-off falling away. Plain shapes and gradients only, so QtSvg (which
+    ignores filters) renders it exactly as other renderers do.
+  -->
+  <!-- Keep this comment inside <svg>: loaders sniff for "<svg" in the first
+       256 bytes, so a long header comment makes the file unrecognisable. -->
   <defs>
     <linearGradient id="backdrop" x1="0" y1="0" x2="0" y2="1">
       <stop offset="0" stop-color="#4cbcf2"/>