diff --git a/crates/typst/src/eval/array.rs b/crates/typst/src/eval/array.rs
index d93b14e62..b98c92968 100644
--- a/crates/typst/src/eval/array.rs
+++ b/crates/typst/src/eval/array.rs
@@ -446,7 +446,7 @@ impl Add for Array {
 }
 
 impl AddAssign for Array {
-    fn add_assign(&mut self, rhs: Array) {
+    fn add_assign(&mut self, rhs: Self) {
         self.0.extend(rhs.0);
     }
 }
diff --git a/crates/typst/src/eval/bytes.rs b/crates/typst/src/eval/bytes.rs
index 5921f485d..2e0c098f9 100644
--- a/crates/typst/src/eval/bytes.rs
+++ b/crates/typst/src/eval/bytes.rs
@@ -1,6 +1,6 @@
 use std::borrow::Cow;
 use std::fmt::{self, Debug, Formatter};
-use std::ops::Deref;
+use std::ops::{Add, AddAssign, Deref};
 use std::sync::Arc;
 
 use comemo::Prehashed;
@@ -96,6 +96,31 @@ impl Debug for Bytes {
     }
 }
 
+impl Add for Bytes {
+    type Output = Self;
+
+    fn add(mut self, rhs: Self) -> Self::Output {
+        self += rhs;
+        self
+    }
+}
+
+impl AddAssign for Bytes {
+    fn add_assign(&mut self, rhs: Self) {
+        if rhs.is_empty() {
+            // Nothing to do
+        } else if self.is_empty() {
+            *self = rhs;
+        } else if Arc::strong_count(&self.0) == 1 && matches!(**self.0, Cow::Owned(_)) {
+            Arc::make_mut(&mut self.0).update(|cow| {
+                cow.to_mut().extend_from_slice(&rhs);
+            })
+        } else {
+            *self = Self::from([self.as_slice(), rhs.as_slice()].concat());
+        }
+    }
+}
+
 impl Serialize for Bytes {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
diff --git a/crates/typst/src/eval/ops.rs b/crates/typst/src/eval/ops.rs
index 323175995..f57f743fa 100644
--- a/crates/typst/src/eval/ops.rs
+++ b/crates/typst/src/eval/ops.rs
@@ -26,6 +26,7 @@ pub fn join(lhs: Value, rhs: Value) -> StrResult<Value> {
         (Str(a), Str(b)) => Str(a + b),
         (Str(a), Symbol(b)) => Str(format_str!("{a}{b}")),
         (Symbol(a), Str(b)) => Str(format_str!("{a}{b}")),
+        (Bytes(a), Bytes(b)) => Bytes(a + b),
         (Content(a), Content(b)) => Content(a + b),
         (Content(a), Symbol(b)) => Content(a + item!(text)(b.get().into())),
         (Content(a), Str(b)) => Content(a + item!(text)(b.into())),
@@ -96,6 +97,7 @@ pub fn add(lhs: Value, rhs: Value) -> StrResult<Value> {
         (Str(a), Str(b)) => Str(a + b),
         (Str(a), Symbol(b)) => Str(format_str!("{a}{b}")),
         (Symbol(a), Str(b)) => Str(format_str!("{a}{b}")),
+        (Bytes(a), Bytes(b)) => Bytes(a + b),
         (Content(a), Content(b)) => Content(a + b),
         (Content(a), Symbol(b)) => Content(a + item!(text)(b.get().into())),
         (Content(a), Str(b)) => Content(a + item!(text)(b.into())),
diff --git a/tests/typ/compiler/bytes.typ b/tests/typ/compiler/bytes.typ
index 32d0d573d..fa724858b 100644
--- a/tests/typ/compiler/bytes.typ
+++ b/tests/typ/compiler/bytes.typ
@@ -12,6 +12,17 @@
 #test(str(bytes(range(0x41, 0x50))), "ABCDEFGHIJKLMNO")
 #test(array(bytes("Hello")), (0x48, 0x65, 0x6C, 0x6C, 0x6F))
 
+---
+// Test addition and joining.
+#test(bytes((1, 2)) + bytes(()), bytes((1, 2)))
+#test(bytes((1, 2)) + bytes((3, 4)), bytes((1, 2, 3, 4)))
+#test(bytes(()) + bytes((3, 4)), bytes((3, 4)))
+#test(str({
+  bytes("Hello")
+  bytes((0x20,))
+  bytes("World")
+}), "Hello World")
+
 ---
 // Error: 8-14 expected string, array, or bytes, found dictionary
 #bytes((a: 1))