diff --git a/crates/annot/src/appearance.rs b/crates/annot/src/appearance.rs
index 9a026069..6a82fbc1 100644
--- a/crates/annot/src/appearance.rs
+++ b/crates/annot/src/appearance.rs
@@ -170,6 +170,10 @@ fn color(d: &Dict, key: &[u8]) -> Option<Option<Rgb>> {
     })
 }
 
+fn interior_color(d: &Dict, fallback: Option<Rgb>) -> Option<Rgb> {
+    color(d, b"IC").flatten().or(fallback)
+}
+
 fn border_width(d: &Dict) -> f64 {
     if let Some(w) = d.get(b"BS").and_then(|b| b.as_dict()).and_then(|b| b.get(b"W")).and_then(|w| w.as_f64()) {
         return w.max(0.0);
@@ -369,7 +373,7 @@ pub fn build(d: &Dict) -> Option<Stream> {
             }
         }
         b"Square" | b"Circle" => {
-            let fill = color(d, b"IC")?;
+            let fill = interior_color(d, None);
             if stroke.is_none() && fill.is_none() {
                 return Some(form(rect, c.as_bytes(), res));
             }
@@ -403,7 +407,7 @@ pub fn build(d: &Dict) -> Option<Stream> {
             if ends.len() != 2 || ends.iter().any(|e| !known_ending(e)) {
                 return None;
             }
-            let fill = color(d, b"IC")?.unwrap_or(col);
+            let fill = interior_color(d, Some(col)).unwrap_or(col);
             c.push_str(&format!("{}{}{} w 1 J 1 j\n{}", rg_stroke(col), rg(fill), n(w), dash(d)));
             c.push_str(&format!("{} {} m {} {} l S\n[] 0 d\n", n(l[0]), n(l[1]), n(l[2]), n(l[3])));
             for (end, (tip, from)) in ends.iter().zip([((l[0], l[1]), (l[2], l[3])), ((l[2], l[3]), (l[0], l[1]))]) {
@@ -417,7 +421,7 @@ pub fn build(d: &Dict) -> Option<Stream> {
             let pts: Vec<(f64, f64)> = v.as_chunks::<2>().0.iter().map(|p| (p[0], p[1])).collect();
             let col = stroke;
             let closed = subtype == b"Polygon";
-            let fill = if closed { color(d, b"IC")? } else { None };
+            let fill = if closed { interior_color(d, None) } else { None };
             let ends = if subtype == b"PolyLine" {
                 match d.get(b"LE") {
                     None => None,
@@ -461,7 +465,7 @@ pub fn build(d: &Dict) -> Option<Stream> {
                 let (Some(start), Some(end)) = (ends.first(), ends.get(1)) else { return None };
                 let (Some(&tip0), Some(&from0)) = (pts.first(), pts.get(1)) else { return None };
                 let (Some(&tip1), Some(&from1)) = (pts.last(), pts.get(pts.len().saturating_sub(2))) else { return None };
-                let fill = color(d, b"IC")?.unwrap_or(col);
+                let fill = interior_color(d, Some(col)).unwrap_or(col);
                 c.push_str(&format!("[] 0 d\n{}", rg(fill)));
                 if !line_end(&mut c, start, tip0, from0, w) || !line_end(&mut c, end, tip1, from1, w) {
                     return None;
diff --git a/crates/annot/src/tests.rs b/crates/annot/src/tests.rs
index 5cd9614a..e7091c51 100644
--- a/crates/annot/src/tests.rs
+++ b/crates/annot/src/tests.rs
@@ -787,6 +787,51 @@ fn line_dict(coords: [f64; 4], ending: &str) -> pdfcraft_cos::Dict {
     d
 }
 
+#[test]
+fn malformed_optional_interior_color_does_not_hide_shape_strokes() {
+    let mut square = pdfcraft_cos::Dict::new();
+    square.set(b"Subtype".to_vec(), Object::name("Square"));
+    square.set(b"Rect".to_vec(), Object::Array([0.0, 0.0, 40.0, 30.0].into_iter().map(Object::Real).collect()));
+    square.set(b"C".to_vec(), Object::Array([1.0, 0.0, 0.0].into_iter().map(Object::Real).collect()));
+    let malformed = Object::Array(vec![Object::Real(1.0), Object::Real(0.0)]);
+    square.set(b"IC".to_vec(), malformed.clone());
+    let mut circle = square.clone();
+    circle.set(b"Subtype".to_vec(), Object::name("Circle"));
+
+    let mut polygon = pdfcraft_cos::Dict::new();
+    polygon.set(b"Subtype".to_vec(), Object::name("Polygon"));
+    polygon.set(b"Rect".to_vec(), Object::Array([0.0, 0.0, 40.0, 30.0].into_iter().map(Object::Real).collect()));
+    polygon.set(b"C".to_vec(), Object::Array([1.0, 0.0, 0.0].into_iter().map(Object::Real).collect()));
+    polygon.set(b"Vertices".to_vec(), Object::Array([0.0, 0.0, 40.0, 0.0, 20.0, 30.0].into_iter().map(Object::Real).collect()));
+    polygon.set(b"IC".to_vec(), malformed.clone());
+
+    let mut line = line_dict([0.0, 0.0, 40.0, 30.0], "None");
+    line.set(b"IC".to_vec(), malformed.clone());
+    let mut polyline = pdfcraft_cos::Dict::new();
+    polyline.set(b"Subtype".to_vec(), Object::name("PolyLine"));
+    polyline.set(b"Rect".to_vec(), Object::Array([0.0, 0.0, 40.0, 30.0].into_iter().map(Object::Real).collect()));
+    polyline.set(b"C".to_vec(), Object::Array([1.0, 0.0, 0.0].into_iter().map(Object::Real).collect()));
+    polyline.set(b"Vertices".to_vec(), Object::Array([0.0, 0.0, 40.0, 0.0, 20.0, 30.0].into_iter().map(Object::Real).collect()));
+    polyline.set(b"LE".to_vec(), Object::Array(vec![Object::name("None"), Object::name("None")]));
+    polyline.set(b"IC".to_vec(), malformed);
+
+    for (name, annotation) in [("Square", square), ("Circle", circle), ("Polygon", polygon), ("Line", line), ("PolyLine", polyline)] {
+        assert!(appearance::build(&annotation).is_some(), "malformed optional /IC must not hide a valid {name} stroke");
+    }
+
+    let doc = document_of(&[
+        b"<< /Type /Catalog /Pages 2 0 R >>",
+        b"<< /Type /Pages /Kids [3 0 R] /Count 1 /MediaBox [0 0 50 40] >>",
+        b"<< /Type /Page /Parent 2 0 R /Annots [4 0 R] >>",
+        b"<< /Type /Annot /Subtype /Square /Rect [5 5 45 35] /C [1 0 0] /IC [1 0] >>",
+    ]);
+    let display = with_missing_appearances(&doc).expect("the valid square gets a fallback appearance");
+    let rendered = list(&display, 0).remove(0);
+    let content = ap_content(&display, &rendered);
+    assert!(content.contains("1 0 0 RG") && content.contains(" re\nS\n"), "the stroke remains drawable without a fill: {content}");
+    assert!(list(&doc, 0)[0].get(b"AP").is_none(), "display generation leaves the source document unchanged");
+}
+
 #[test]
 fn every_line_ending_is_drawn() {
     let filled = [LineEnding::Square, LineEnding::Circle, LineEnding::Diamond, LineEnding::ClosedArrow, LineEnding::RClosedArrow];