diff --git a/crates/forms/src/appearance.rs b/crates/forms/src/appearance.rs
index 651f8e3208..9b52c5a33e 100644
--- a/crates/forms/src/appearance.rs
+++ b/crates/forms/src/appearance.rs
@@ -460,6 +460,8 @@ pub enum Overflow {
     Wide { width: f64, room: f64, size: f64 },
     /// `lines` wrapped lines, of which the box shows `room`, at `size` points.
     Tall { lines: usize, room: usize, size: f64 },
+    /// One line `height` points high (ascent to descent), with `room` for it, at `size` points.
+    High { height: f64, room: f64, size: f64 },
 }
 
 impl std::fmt::Display for Overflow {
@@ -469,6 +471,9 @@ impl std::fmt::Display for Overflow {
                 write!(f, "the value does not fit: {} pt wide at {} pt, room for {} pt", fmt(*width), fmt(*size), fmt(*room))
             }
             Self::Tall { lines, room, size } => write!(f, "the value does not fit: {lines} lines at {} pt, room for {room}", fmt(*size)),
+            Self::High { height, room, size } => {
+                write!(f, "the value does not fit: {} pt high at {} pt, room for {} pt", fmt(*height), fmt(*size), fmt(*room))
+            }
         }
     }
 }
@@ -589,6 +594,9 @@ fn field_appearance_fit(doc: &Document, f: &Field, w: &Widget, values: &[String]
                 }
                 if room < lines.len() {
                     overflow = Some(Overflow::Tall { lines: lines.len(), room, size });
+                } else if let Some(tw) = lines.iter().map(|l| width_of(l, size)).filter(|tw| *tw > inner_w + 0.01).reduce(f64::max) {
+                    // A character wider than the box is a line of its own, still cut at the sides.
+                    overflow = Some(Overflow::Wide { width: tw, room: inner_w, size });
                 }
             } else {
                 if size == 0.0 {
@@ -601,6 +609,11 @@ fn field_appearance_fit(doc: &Document, f: &Field, w: &Widget, values: &[String]
                 }
                 // Centre Helvetica's ascent (0.718) and descent (0.207) vertically.
                 let y = (height - 0.925 * size) / 2.0 + 0.207 * size;
+                // The clip box is inside the border; a line taller than it is cut at the top and bottom.
+                let room_h = height - 2.0 * bw;
+                if 0.925 * size > room_h + 0.01 {
+                    overflow = Some(Overflow::High { height: 0.925 * size, room: room_h, size });
+                }
                 if comb {
                     let cells = f.max_len.unwrap_or(1).max(1);
                     let cell = width / cells as f64;
@@ -610,7 +623,7 @@ fn field_appearance_fit(doc: &Document, f: &Field, w: &Widget, values: &[String]
                     }
                 } else {
                     let tw = width_of(&text.replace(['\n', '\r'], " "), size);
-                    if tw > inner_w + 0.01 {
+                    if overflow.is_none() && tw > inner_w + 0.01 {
                         overflow = Some(Overflow::Wide { width: tw, room: inner_w, size });
                     }
                     show(&mut body, x_for(&text, size), y, &text);
@@ -643,6 +656,8 @@ fn field_appearance_fit(doc: &Document, f: &Field, w: &Widget, values: &[String]
     d.set(b"Subtype".to_vec(), Object::name("Form"));
     set_form_box(&mut d, place);
     d.set(b"Resources".to_vec(), Object::Dict(res));
+    // Nothing drawn is nothing cut, however small the box.
+    let overflow = overflow.filter(|_| !text.is_empty());
     (Stream::flate(d, &content), unencodable, overflow)
 }
 
diff --git a/crates/forms/src/tests.rs b/crates/forms/src/tests.rs
index 84ce879847..237b9d1092 100644
--- a/crates/forms/src/tests.rs
+++ b/crates/forms/src/tests.rs
@@ -3018,3 +3018,50 @@ fn a_value_wider_or_taller_than_its_box_is_reported() {
     assert_eq!(overflow("wide"), None);
     assert_eq!(overflow("short"), None);
 }
+
+/// #4018: a single line taller than its box is cut at the top and bottom, and a character wider
+/// than a multiline box is a line of its own that is still cut at the sides; both are reported.
+/// An empty value draws nothing, so nothing is cut however small the box.
+#[test]
+fn a_line_taller_than_its_box_or_a_character_wider_than_it_is_reported() {
+    let field = |name: &str, rect: &str, extra: &str, value: &str| {
+        format!("<< /Type /Annot /Subtype /Widget /FT /Tx /T ({name}) /V ({value}) /Rect [{rect}] /P 3 0 R {extra} >>")
+    };
+    let doc = document(&[
+        "<< /Type /Catalog /Pages 2 0 R /AcroForm 4 0 R >>".into(),
+        "<< /Type /Pages /Kids [3 0 R] /Count 1 /MediaBox [0 0 600 800] >>".into(),
+        "<< /Type /Page /Parent 2 0 R /Annots [6 0 R 7 0 R 8 0 R 9 0 R 10 0 R 11 0 R] >>".into(),
+        "<< /Fields [6 0 R 7 0 R 8 0 R 9 0 R 10 0 R 11 0 R] /DA (/Helv 12 Tf 0 g) /DR << /Font << /Helv 5 0 R >> >> >>".into(),
+        "<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica /Encoding /WinAnsiEncoding >>".into(),
+        field("low", "50 700 190 708", "", "Ada"),
+        field("comb", "50 650 190 658", "/Ff 16777216 /MaxLen 5", "Ada"),
+        field("narrow", "50 500 56 560", "/Ff 4096", "WW"),
+        field("roomy", "50 400 190 418", "", "Ada"),
+        field("empty", "50 350 190 358", "", ""),
+        field("empty-multi", "50 300 190 304", "/Ff 4096", ""),
+    ]);
+    let overflow = |name: &str| {
+        let f = fields(&doc).into_iter().find(|f| f.name == name).unwrap();
+        appearance::value_overflow(&doc, &f, &f.widgets[0])
+    };
+    for name in ["low", "comb"] {
+        match overflow(name) {
+            Some(o @ appearance::Overflow::High { height, room, size }) => {
+                assert_eq!(size, 12.0);
+                assert!((height - 11.1).abs() < 0.01 && room <= 8.0, "{name}: {height} in {room}");
+                assert!(o.to_string().starts_with("the value does not fit: 11.1 pt high at 12 pt"), "{o}");
+            }
+            other => panic!("{name}: {other:?}"),
+        }
+    }
+    match overflow("narrow") {
+        Some(appearance::Overflow::Wide { width, room, size }) => {
+            assert_eq!(size, 12.0);
+            assert!(width > room && (width - 11.32).abs() < 0.1, "{width} in {room}");
+        }
+        other => panic!("narrow: {other:?}"),
+    }
+    assert_eq!(overflow("roomy"), None);
+    assert_eq!(overflow("empty"), None);
+    assert_eq!(overflow("empty-multi"), None);
+}