diff --git a/tracing-core/src/callsite.rs b/tracing-core/src/callsite.rs
index 3a0ccd02ff..273fecec4e 100644
--- a/tracing-core/src/callsite.rs
+++ b/tracing-core/src/callsite.rs
@@ -15,7 +15,6 @@ use crate::{
     dispatcher::Dispatch,
     metadata::{LevelFilter, Metadata},
     subscriber::Interest,
-    Once,
 };
 
 use self::dispatchers::Dispatchers;
diff --git a/tracing-core/src/dispatcher.rs b/tracing-core/src/dispatcher.rs
index f81a6c463e..741744437c 100644
--- a/tracing-core/src/dispatcher.rs
+++ b/tracing-core/src/dispatcher.rs
@@ -134,7 +134,7 @@ use crate::stdlib::{
     fmt,
     sync::{
         atomic::{AtomicBool, AtomicUsize, Ordering},
-        Arc, Weak,
+        Arc,
     },
 };
 
@@ -142,6 +142,7 @@ use crate::stdlib::{
 use crate::stdlib::{
     cell::{Cell, RefCell, RefMut},
     error,
+    sync::Weak,
 };
 
 /// `Dispatch` trace data to a [`Subscriber`].
@@ -387,6 +388,7 @@ fn get_global() -> Option<&'static Dispatch> {
     }
 }
 
+#[cfg(feature = "std")]
 pub(crate) struct Registrar(Weak<dyn Subscriber + Send + Sync>);
 
 impl Dispatch {
@@ -412,6 +414,7 @@ impl Dispatch {
         me
     }
 
+    #[cfg(feature = "std")]
     pub(crate) fn registrar(&self) -> Registrar {
         Registrar(Arc::downgrade(&self.subscriber))
     }
@@ -651,6 +654,7 @@ where
     }
 }
 
+#[cfg(feature = "std")]
 impl Registrar {
     pub(crate) fn upgrade(&self) -> Option<Dispatch> {
         self.0.upgrade().map(|subscriber| Dispatch { subscriber })