diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index 97b73fac1a42..8d3215e69cd2 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -71,8 +71,8 @@ pub struct Session {
     pub parse_sess: ParseSess,
     /// For a library crate, this is always none
     pub entry_fn: Once<Option<(NodeId, Span, config::EntryFnType)>>,
-    pub plugin_registrar_fn: Cell<Option<ast::NodeId>>,
-    pub derive_registrar_fn: Cell<Option<ast::NodeId>>,
+    pub plugin_registrar_fn: Once<Option<ast::NodeId>>,
+    pub derive_registrar_fn: Once<Option<ast::NodeId>>,
     pub default_sysroot: Option<PathBuf>,
     /// The name of the root source file of the crate, in the local file system.
     /// `None` means that there is no source file.
@@ -1094,8 +1094,8 @@ pub fn build_session_(
         parse_sess: p_s,
         // For a library crate, this is always none
         entry_fn: Once::new(),
-        plugin_registrar_fn: Cell::new(None),
-        derive_registrar_fn: Cell::new(None),
+        plugin_registrar_fn: Once::new(),
+        derive_registrar_fn: Once::new(),
         default_sysroot,
         local_crate_source_file,
         working_dir,
diff --git a/src/librustc_trans/back/symbol_export.rs b/src/librustc_trans/back/symbol_export.rs
index acd2a7657307..965a34eccb86 100644
--- a/src/librustc_trans/back/symbol_export.rs
+++ b/src/librustc_trans/back/symbol_export.rs
@@ -157,12 +157,12 @@ fn reachable_non_generics_provider<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         })
         .collect();
 
-    if let Some(id) = tcx.sess.derive_registrar_fn.get() {
+    if let Some(id) = *tcx.sess.derive_registrar_fn.get() {
         let def_id = tcx.hir.local_def_id(id);
         reachable_non_generics.insert(def_id, SymbolExportLevel::C);
     }
 
-    if let Some(id) = tcx.sess.plugin_registrar_fn.get() {
+    if let Some(id) = *tcx.sess.plugin_registrar_fn.get() {
         let def_id = tcx.hir.local_def_id(id);
         reachable_non_generics.insert(def_id, SymbolExportLevel::C);
     }
diff --git a/src/librustc_trans_utils/symbol_names.rs b/src/librustc_trans_utils/symbol_names.rs
index af174f7ce851..f3b7326b2107 100644
--- a/src/librustc_trans_utils/symbol_names.rs
+++ b/src/librustc_trans_utils/symbol_names.rs
@@ -244,11 +244,11 @@ fn compute_symbol_name<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, instance: Instance
     let node_id = tcx.hir.as_local_node_id(def_id);
 
     if let Some(id) = node_id {
-        if tcx.sess.plugin_registrar_fn.get() == Some(id) {
+        if *tcx.sess.plugin_registrar_fn.get() == Some(id) {
             let disambiguator = tcx.sess.local_crate_disambiguator();
             return tcx.sess.generate_plugin_registrar_symbol(disambiguator);
         }
-        if tcx.sess.derive_registrar_fn.get() == Some(id) {
+        if *tcx.sess.derive_registrar_fn.get() == Some(id) {
             let disambiguator = tcx.sess.local_crate_disambiguator();
             return tcx.sess.generate_derive_registrar_symbol(disambiguator);
         }