diff --git a/src/proc/constant_evaluator.rs b/src/proc/constant_evaluator.rs
index c3796ccc69..61adf0fdd5 100644
--- a/src/proc/constant_evaluator.rs
+++ b/src/proc/constant_evaluator.rs
@@ -1158,9 +1158,11 @@ impl<'a> ConstantEvaluator<'a> {
         expr: Expression,
         span: Span,
     ) -> Result<Handle<Expression>, ConstantEvaluatorError> {
-        match expr {
-            Expression::Literal(literal) => crate::valid::validate_literal(literal)?,
-            _ => {}
+        // It suffices to only check literals, since we only register one
+        // expression at a time, `Compose` expressions can only refer to other
+        // expressions, and `ZeroValue` expressions are always okay.
+        if let Expression::Literal(literal) = expr {
+            crate::valid::validate_literal(literal)?;
         }
 
         if let Some(FunctionLocalData {