diff --git a/hugr-core/src/std_extensions/arithmetic/int_types.rs b/hugr-core/src/std_extensions/arithmetic/int_types.rs
index 6ec3b7724..522f8b2b9 100644
--- a/hugr-core/src/std_extensions/arithmetic/int_types.rs
+++ b/hugr-core/src/std_extensions/arithmetic/int_types.rs
@@ -87,7 +87,7 @@ const fn type_arg(log_width: u8) -> TypeArg {
 }
 
 /// An integer (either signed or unsigned)
-#[derive(Clone, Debug, Eq, PartialEq, serde::Serialize, serde::Deserialize)]
+#[derive(Clone, Debug, Eq, PartialEq, Hash, serde::Serialize, serde::Deserialize)]
 pub struct ConstInt {
     log_width: u8,
     // We always use a u64 for the value. The interpretation is: