diff --git a/src/protocol/ast.rs b/src/protocol/ast.rs
index 6b94de786baa4d6499717d8cb2949e119babfe62..560ffe71caf14fc10a9c50fbb723d3b565fb0f25 100644
--- a/src/protocol/ast.rs
+++ b/src/protocol/ast.rs
@@ -405,7 +405,7 @@ impl ImportedDeclarationId {
     }
 }
 
-#[derive(serde::Serialize, serde::Deserialize)]
+#[derive(Debug, serde::Serialize, serde::Deserialize)]
 pub struct Heap {
     // Phase 0: allocation
     protocol_descriptions: Arena<Root>,