diff --git a/crates/typst/src/eval/ops.rs b/crates/typst/src/eval/ops.rs
index 4a64cfed7..093eaa5f3 100644
--- a/crates/typst/src/eval/ops.rs
+++ b/crates/typst/src/eval/ops.rs
@@ -52,6 +52,16 @@ pub fn pos(value: Value) -> StrResult<Value> {
         Ratio(v) => Ratio(v),
         Relative(v) => Relative(v),
         Fraction(v) => Fraction(v),
+        Symbol(_) | Str(_) | Bytes(_) | Content(_) | Array(_) | Dict(_) | Datetime(_) => {
+            mismatch!("cannot apply unary '+' to {}", value)
+        }
+        Dyn(d) => {
+            if d.is::<Align>() {
+                mismatch!("cannot apply unary '+' to {}", d)
+            } else {
+                mismatch!("cannot apply '+' to {}", d)
+            }
+        }
         v => mismatch!("cannot apply '+' to {}", v),
     })
 }
@@ -67,6 +77,7 @@ pub fn neg(value: Value) -> StrResult<Value> {
         Relative(v) => Relative(-v),
         Fraction(v) => Fraction(-v),
         Duration(v) => Duration(-v),
+        Datetime(_) => mismatch!("cannot apply unary '-' to {}", value),
         v => mismatch!("cannot apply '-' to {}", v),
     })
 }
diff --git a/tests/typ/compiler/ops-invalid.typ b/tests/typ/compiler/ops-invalid.typ
index 7e8b63eff..de8e62346 100644
--- a/tests/typ/compiler/ops-invalid.typ
+++ b/tests/typ/compiler/ops-invalid.typ
@@ -14,7 +14,7 @@
 #test({2*}, 2)
 
 ---
-// Error: 3-13 cannot apply '+' to content
+// Error: 3-13 cannot apply unary '+' to content
 #(+([] + []))
 
 ---