diff --git a/crates/optimize/src/images.rs b/crates/optimize/src/images.rs
index 51c130abd8..7666c036fc 100644
--- a/crates/optimize/src/images.rs
+++ b/crates/optimize/src/images.rs
@@ -1102,7 +1102,10 @@ fn mono(doc: &Document, s: &Stream, ppi: f64, defaults: bool, settings: &MonoSet
     // JBIG2 (whose symbols may be smaller than its own coding) can be smaller stored again alone.
     let alone_to_g4 = s.filters().len() == 1 && settings.compression == MonoCompression::CcittG4;
     let only_to_resample = retain || (alone_to_g4 && (jbig2 || fax.is_some_and(|p| p.k < 0)));
-    if only_to_resample && !downsample {
+    // What can't be averaged, whatever it holds, comes to the same `None` below, after a decode that
+    // would spend the run's allowance on it.
+    let too_wide = d.int(b"Width").is_some_and(|w| w > i64::from(pdfcraft_filters::MAX_CCITT_COLUMNS));
+    if only_to_resample && (!downsample || defaults || too_wide || (jbig2 && dark_is_one(doc, d).is_none())) {
         return None;
     }
     let (data, w, h, packed) = one_bit(doc, s, !retain, defaults, budget)?;
@@ -1398,6 +1401,36 @@ mod dimension_tests {
         assert_eq!(changed, 2, "the third is as it was");
     }
 
+    /// Decoded only to be resampled, what can't be averaged whatever it holds isn't decoded, so it
+    /// takes nothing from the images that can be, and isn't counted as refused past the allowance.
+    #[test]
+    fn a_jbig2_image_that_cant_be_averaged_spends_nothing() {
+        let image = |edit: &dyn Fn(&mut Dict)| {
+            let mut dict = Dict::new();
+            dict.set(b"Subtype".to_vec(), Object::name("Image"));
+            dict.set(b"Width".to_vec(), Object::Int(16));
+            dict.set(b"Height".to_vec(), Object::Int(2));
+            dict.set(b"BitsPerComponent".to_vec(), Object::Int(1));
+            dict.set(b"ColorSpace".to_vec(), Object::name("DeviceGray"));
+            dict.set(b"Filter".to_vec(), Object::name("JBIG2Decode"));
+            edit(&mut dict);
+            Stream::from_raw(dict, pdfcraft_filters::encode_jbig2_generic(&[0xF0; 4], 16, 2).unwrap())
+        };
+        let settings = MonoSettings { compression: MonoCompression::Retain, ..MonoSettings::REDUCE };
+        let spent = |s: &Stream, defaults: bool| {
+            let mut budget = ImageBudget::with_work(u64::MAX);
+            let _ = mono(&Document::new_empty(), s, 720.0, defaults, &settings, &mut budget);
+            u64::MAX - budget.work_left()
+        };
+        let plain = image(&|_| {});
+        assert!(spent(&plain, false) > 0, "one that can be averaged is decoded");
+        assert_eq!(spent(&plain, true), 0, "drawn where a device colour space is remapped");
+        let wide = image(&|d| d.set(b"Width".to_vec(), Object::Int(i64::from(pdfcraft_filters::MAX_CCITT_COLUMNS) + 1)));
+        assert_eq!(spent(&wide, false), 0, "too wide to average");
+        let tinted = image(&|d| d.set(b"ColorSpace".to_vec(), Object::Array(vec![Object::name("CalGray"), Object::Dict(Dict::new())])));
+        assert_eq!(spent(&tinted, false), 0, "no way to tell which sample is dark");
+    }
+
     /// A JPEG larger than its dictionary says is refused from its header, before its pixels are decoded.
     #[test]
     fn a_jpeg_of_another_size_than_its_dictionary_is_not_decoded() {
diff --git a/crates/redact/src/image.rs b/crates/redact/src/image.rs
index 2880bd2304..52377078be 100644
--- a/crates/redact/src/image.rs
+++ b/crates/redact/src/image.rs
@@ -59,13 +59,19 @@ fn decode_and_clear(doc: &Document, s: &Stream, ctm: &Matrix, rects: &[[f64; 4]]
     let fax = |f: &Object| f.as_name().is_some_and(|n| matches!(n, b"CCITTFaxDecode" | b"CCF"));
     let jbig2 = |f: &Object| f.as_name() == Some(b"JBIG2Decode".as_slice());
     let readable = |f: &Object| f.as_name().is_some_and(supported);
+    // `/Crypt` was undone when the object was loaded (ISO 32000-2 §7.4.10), and decoding leaves it
+    // out wherever it stands.
+    let crypt = |f: &Object| f.as_name() == Some(b"Crypt".as_slice());
     let (ok, is_fax, is_jbig2) = match s.dict.get(b"Filter") {
         None => (true, false, false),
-        Some(f @ Object::Name(_)) => (readable(f) || fax(f) || jbig2(f), fax(f), jbig2(f)),
-        Some(Object::Array(a)) => match a.split_last() {
-            Some((last, before)) if fax(last) || jbig2(last) => (before.iter().all(readable), fax(last), jbig2(last)),
-            _ => (a.iter().all(readable), false, false),
-        },
+        Some(f @ Object::Name(_)) => (readable(f) || crypt(f) || fax(f) || jbig2(f), fax(f), jbig2(f)),
+        Some(Object::Array(a)) => {
+            let chain: Vec<&Object> = a.iter().filter(|f| !crypt(f)).collect();
+            match chain.split_last() {
+                Some((last, before)) if fax(last) || jbig2(last) => (before.iter().all(|f| readable(f)), fax(last), jbig2(last)),
+                _ => (chain.iter().all(|f| readable(f)), false, false),
+            }
+        }
         _ => (false, false, false),
     };
     if !ok {
diff --git a/crates/redact/src/tests.rs b/crates/redact/src/tests.rs
index a14dffdb98..a547193dce 100644
--- a/crates/redact/src/tests.rs
+++ b/crates/redact/src/tests.rs
@@ -804,6 +804,13 @@ fn a_jbig2_image_has_its_covered_pixels_cleared_instead_of_being_removed() {
         (
             format!("{image} /ColorSpace /DeviceGray /Filter [/ASCIIHexDecode /JBIG2Decode] /DecodeParms [null << /JBIG2Globals 8 0 R >>]"),
             hex,
+            vec![globals.clone()],
+            [0x00, 0xFF, 0xFF, 0xFF],
+        ),
+        // `/Crypt` was undone on load, and takes a place in the parameters.
+        (
+            format!("{image} /ColorSpace /DeviceGray /Filter [/Crypt /JBIG2Decode] /DecodeParms [null << /JBIG2Globals 8 0 R >>]"),
+            white.clone(),
             vec![globals],
             [0x00, 0xFF, 0xFF, 0xFF],
         ),