diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 2b989ee2952..41bd63d68a5 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1048,7 +1048,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         };
 
         record!(self.tables.kind[def_id] <- EntryKind::Variant(self.lazy(data)));
-        record!(self.tables.impl_constness[def_id] <- hir::Constness::Const);
+        self.tables.impl_constness.set(def_id.index, hir::Constness::Const);
         record!(self.tables.children[def_id] <- variant.fields.iter().map(|f| {
             assert!(f.did.is_local());
             f.did.index
@@ -1078,7 +1078,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         };
 
         record!(self.tables.kind[def_id] <- EntryKind::Variant(self.lazy(data)));
-        record!(self.tables.impl_constness[def_id] <- hir::Constness::Const);
+        self.tables.impl_constness.set(def_id.index, hir::Constness::Const);
         self.encode_item_type(def_id);
         if variant.ctor_kind == CtorKind::Fn {
             record!(self.tables.fn_sig[def_id] <- tcx.fn_sig(def_id));
@@ -1157,7 +1157,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         };
 
         record!(self.tables.repr_options[def_id] <- adt_def.repr());
-        record!(self.tables.impl_constness[def_id] <- hir::Constness::Const);
+        self.tables.impl_constness.set(def_id.index, hir::Constness::Const);
         record!(self.tables.kind[def_id] <- EntryKind::Struct(self.lazy(data)));
         self.encode_item_type(def_id);
         if variant.ctor_kind == CtorKind::Fn {
@@ -1208,7 +1208,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                     }
                 };
                 record!(self.tables.asyncness[def_id] <- m_sig.header.asyncness);
-                record!(self.tables.impl_constness[def_id] <- hir::Constness::NotConst);
+                self.tables.impl_constness.set(def_id.index, hir::Constness::NotConst);
                 record!(self.tables.kind[def_id] <- EntryKind::AssocFn(self.lazy(AssocFnData {
                     container,
                     has_self: trait_item.fn_has_self_parameter,
@@ -1273,7 +1273,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 } else {
                     hir::Constness::NotConst
                 };
-                record!(self.tables.impl_constness[def_id] <- constness);
+                self.tables.impl_constness.set(def_id.index, constness);
                 record!(self.tables.kind[def_id] <- EntryKind::AssocFn(self.lazy(AssocFnData {
                     container,
                     has_self: impl_item.fn_has_self_parameter,
@@ -1396,7 +1396,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             hir::ItemKind::Fn(ref sig, .., body) => {
                 record!(self.tables.asyncness[def_id] <- sig.header.asyncness);
                 record!(self.tables.fn_arg_names[def_id] <- self.tcx.hir().body_param_names(body));
-                record!(self.tables.impl_constness[def_id] <- sig.header.constness);
+                self.tables.impl_constness.set(def_id.index, sig.header.constness);
                 EntryKind::Fn
             }
             hir::ItemKind::Macro(ref macro_def, _) => {
@@ -1420,7 +1420,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             hir::ItemKind::Struct(ref struct_def, _) => {
                 let adt_def = self.tcx.adt_def(def_id);
                 record!(self.tables.repr_options[def_id] <- adt_def.repr());
-                record!(self.tables.impl_constness[def_id] <- hir::Constness::Const);
+                self.tables.impl_constness.set(def_id.index, hir::Constness::Const);
 
                 // Encode def_ids for each field and method
                 // for methods, write all the stuff get_trait_method
@@ -1451,7 +1451,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             }
             hir::ItemKind::Impl(hir::Impl { defaultness, constness, .. }) => {
                 record!(self.tables.impl_defaultness[def_id] <- defaultness);
-                record!(self.tables.impl_constness[def_id] <- constness);
+                self.tables.impl_constness.set(def_id.index, constness);
 
                 let trait_ref = self.tcx.impl_trait_ref(def_id);
                 if let Some(trait_ref) = trait_ref {
@@ -1893,7 +1893,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 } else {
                     hir::Constness::NotConst
                 };
-                record!(self.tables.impl_constness[def_id] <- constness);
+                self.tables.impl_constness.set(def_id.index, constness);
                 record!(self.tables.kind[def_id] <- EntryKind::ForeignFn);
             }
             hir::ForeignItemKind::Static(..) => {
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index ffd21767f5c..4dd000eaefe 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -311,7 +311,7 @@ define_tables! {
     thir_abstract_const: Table<DefIndex, Lazy!(&'tcx [thir::abstract_const::Node<'tcx>])>,
     impl_parent: Table<DefIndex, Lazy!(DefId)>,
     impl_polarity: Table<DefIndex, ty::ImplPolarity>,
-    impl_constness: Table<DefIndex, Lazy!(hir::Constness)>,
+    impl_constness: Table<DefIndex, hir::Constness>,
     impl_defaultness: Table<DefIndex, Lazy!(hir::Defaultness)>,
     // FIXME(eddyb) perhaps compute this on the fly if cheap enough?
     coerce_unsized_info: Table<DefIndex, Lazy!(ty::adjustment::CoerceUnsizedInfo)>,
diff --git a/compiler/rustc_metadata/src/rmeta/table.rs b/compiler/rustc_metadata/src/rmeta/table.rs
index ca76afeffe0..6bb07a34e0f 100644
--- a/compiler/rustc_metadata/src/rmeta/table.rs
+++ b/compiler/rustc_metadata/src/rmeta/table.rs
@@ -113,6 +113,13 @@ fixed_size_enum! {
     }
 }
 
+fixed_size_enum! {
+    hir::Constness {
+        ( NotConst )
+        ( Const    )
+    }
+}
+
 // NOTE(eddyb) there could be an impl for `usize`, which would enable a more
 // generic `Lazy<T>` impl, but in the general case we might not need / want to
 // fit every `usize` in `u32`.