diff --git a/crates/engine/src/cmd/fileio/jxlread.rs b/crates/engine/src/cmd/fileio/jxlread.rs
index 9e0a0b64c..1d4e3d138 100644
--- a/crates/engine/src/cmd/fileio/jxlread.rs
+++ b/crates/engine/src/cmd/fileio/jxlread.rs
@@ -4,10 +4,10 @@
 //!
 //! Colors come back as sRGB whenever the decoder converts them without a color management
 //! system: XYB-encoded images, every color space a JPEG XL header names, and embedded ICC
-//! profiles that describe one of them. Any other image with an embedded ICC profile comes back
-//! with its samples as stored, as PNG and JPEG files with an embedded profile are drawn, and with
-//! the profile when it is an RGB one. Gray images with an ICC profile the decoder cannot convert
-//! are refused. 16-bit and floating-point samples become 8 bits, alpha comes back straight,
+//! profiles that describe one of them. Any other image with an embedded RGB ICC profile comes
+//! back with its samples as stored, as PNG and JPEG files with an embedded profile are drawn, and
+//! with the profile. Gray images, and images whose profile is not an RGB one, are refused when the
+//! decoder cannot convert their ICC profile. 16-bit and floating-point samples become 8 bits, alpha comes back straight,
 //! and CMYK images are refused. The file is untrusted: the decoder is given only a container's
 //! image boxes, the image's size is checked from its header before any pixels are decoded, and the
 //! decoder's image buffers are capped.
@@ -235,13 +235,17 @@ fn to_srgb_without_cms(xyb: bool, icc: Option<&[u8]>) -> bool {
 }
 
 /// The embedded RGB profile when the decoder leaves colors in it. Gray colors without a
-/// conversion to sRGB cannot be stored as RGB without changing their profile.
+/// conversion to sRGB cannot be stored as RGB without changing their profile, and neither can
+/// colors left in a profile that is not an RGB one.
 pub(crate) fn output_profile(xyb: bool, grayscale: bool, icc: Option<&[u8]>) -> Result<Option<Vec<u8>>, String> {
     let converts = to_srgb_without_cms(xyb, icc);
     if grayscale && !converts {
         return Err(unreadable("unsupported grayscale ICC profile"));
     }
-    Ok(icc.filter(|icc| icc.get(16..20) == Some(b"RGB ") && !converts).map(<[u8]>::to_vec))
+    if !converts && icc.and_then(|icc| icc.get(16..20)) != Some(b"RGB ") {
+        return Err(unreadable("unsupported ICC profile color space"));
+    }
+    Ok(icc.filter(|_| !converts).map(<[u8]>::to_vec))
 }
 
 /// The decoder's error `e` as a message. When the decoder's buffers needed more than they were
diff --git a/crates/engine/src/cmd/fileio/tests_jxlread.rs b/crates/engine/src/cmd/fileio/tests_jxlread.rs
index 1774cb3a2..6e6af80c8 100644
--- a/crates/engine/src/cmd/fileio/tests_jxlread.rs
+++ b/crates/engine/src/cmd/fileio/tests_jxlread.rs
@@ -295,6 +295,11 @@ fn colors_left_in_their_icc_profile_keep_it() {
         None
     );
     assert_eq!(output_profile(false, false, None).unwrap(), None);
+    // A color image left in a profile that is not an RGB one can't be stored as RGB.
+    let mut lab = rgb.clone();
+    lab[16..20].copy_from_slice(b"Lab ");
+    assert_eq!(output_profile(false, false, Some(&lab)).unwrap_err(), "the JPEG XL file can't be read: unsupported ICC profile color space");
+    assert_eq!(output_profile(true, false, Some(&lab)).unwrap(), None, "XYB-encoded colors become sRGB");
     // The PNG carries the profile, the pixels and the resolution.
     let img = image::RgbaImage::from_raw(2, 1, vec![200, 100, 50, 255, 9, 9, 9, 0]).unwrap();
     for icc in [Some(rgb), None] {