diff --git a/src/eval/walk.rs b/src/eval/walk.rs
index 7ffb4c050..3b9fc0940 100644
--- a/src/eval/walk.rs
+++ b/src/eval/walk.rs
@@ -5,6 +5,7 @@ use crate::diag::TypResult;
 use crate::geom::Gen;
 use crate::layout::{ParChild, ParNode, StackChild, StackNode};
 use crate::syntax::*;
+use crate::util::BoolExt;
 
 /// Walk a syntax node and fill the currently built template.
 pub trait Walk {
@@ -27,8 +28,8 @@ impl Walk for SyntaxNode {
             Self::Space => ctx.template.space(),
             Self::Linebreak(_) => ctx.template.linebreak(),
             Self::Parbreak(_) => ctx.template.parbreak(),
-            Self::Strong(_) => ctx.template.modify(|s| s.font_mut().strong ^= true),
-            Self::Emph(_) => ctx.template.modify(|s| s.font_mut().emph ^= true),
+            Self::Strong(_) => ctx.template.modify(|s| s.font_mut().strong.flip()),
+            Self::Emph(_) => ctx.template.modify(|s| s.font_mut().emph.flip()),
             Self::Text(text) => ctx.template.text(text),
             Self::Raw(raw) => raw.walk(ctx)?,
             Self::Heading(heading) => heading.walk(ctx)?,
diff --git a/src/util/mod.rs b/src/util/mod.rs
index 3608ca767..1abdcbc92 100644
--- a/src/util/mod.rs
+++ b/src/util/mod.rs
@@ -11,6 +11,18 @@ use std::cmp::Ordering;
 use std::ops::Range;
 use std::path::{Component, Path, PathBuf};
 
+/// Additional methods for booleans.
+pub trait BoolExt {
+    /// Toggle the value of the bool in place.
+    fn flip(&mut self);
+}
+
+impl BoolExt for bool {
+    fn flip(&mut self) {
+        *self = !*self;
+    }
+}
+
 /// Additional methods for options.
 pub trait OptionExt<T> {
     /// Replace `self` with `other` if `self` is `Some`.