diff --git a/src/librustc/ich/impls_ty.rs b/src/librustc/ich/impls_ty.rs
index 74441d469456..4f691c0d3948 100644
--- a/src/librustc/ich/impls_ty.rs
+++ b/src/librustc/ich/impls_ty.rs
@@ -368,6 +368,17 @@ impl_stable_hash_for!(struct mir::interpret::MemoryPointer {
     offset
 });
 
+enum AllocDiscriminant {
+    Static,
+    Constant,
+    Function,
+}
+impl_stable_hash_for!(enum self::AllocDiscriminant {
+    Static,
+    Constant,
+    Function
+});
+
 impl<'a> HashStable<StableHashingContext<'a>> for mir::interpret::AllocId {
     fn hash_stable<W: StableHasherResult>(
         &self,
@@ -377,15 +388,15 @@ impl<'a> HashStable<StableHashingContext<'a>> for mir::interpret::AllocId {
         ty::tls::with_opt(|tcx| {
             let tcx = tcx.expect("can't hash AllocIds during hir lowering");
             if let Some(def_id) = tcx.interpret_interner.get_corresponding_static_def_id(*self) {
-                0.hash_stable(hcx, hasher);
+                AllocDiscriminant::Static.hash_stable(hcx, hasher);
                 // statics are unique via their DefId
                 def_id.hash_stable(hcx, hasher);
             } else if let Some(alloc) = tcx.interpret_interner.get_alloc(*self) {
                 // not a static, can't be recursive, hash the allocation
-                1.hash_stable(hcx, hasher);
+                AllocDiscriminant::Constant.hash_stable(hcx, hasher);
                 alloc.hash_stable(hcx, hasher);
             } else if let Some(inst) = tcx.interpret_interner.get_fn(*self) {
-                2.hash_stable(hcx, hasher);
+                AllocDiscriminant::Function.hash_stable(hcx, hasher);
                 inst.hash_stable(hcx, hasher);
             } else {
                 bug!("no allocation for {}", self);