diff --git a/bon-macros/src/builder/builder_gen/builder_decl.rs b/bon-macros/src/builder/builder_gen/builder_decl.rs
index 474fae43..f25c4256 100644
--- a/bon-macros/src/builder/builder_gen/builder_decl.rs
+++ b/bon-macros/src/builder/builder_gen/builder_decl.rs
@@ -70,8 +70,15 @@ impl super::BuilderGenCtx {
         let docs = &self.builder_type.docs;
         let state_var = &self.state_var;
 
-        let custom_fields_idents = self.custom_fields().map(|field| &field.ident);
-        let custom_fields_types = self.custom_fields().map(|field| &field.norm_ty);
+        let custom_fields = self.custom_fields().map(|field| {
+            let ident = &field.ident;
+            let ty = &field.norm_ty;
+            let doc = format!("Private builder field `{ident}` for use in custom methods.");
+            quote! {
+                #[doc = #doc]
+                #ident: #ty
+            }
+        });
 
         quote! {
             #[must_use = #must_use_message]
@@ -109,7 +116,7 @@ impl super::BuilderGenCtx {
 
                 #( #start_fn_args_fields, )*
 
-                #( #custom_fields_idents: #custom_fields_types, )*
+                #( #custom_fields, )*
 
                 #private_field_attrs
                 __unsafe_private_named: (
diff --git a/bon-sandbox/src/docs_in_private_items.rs b/bon-sandbox/src/docs_in_private_items.rs
index d1ae5b7b..ba4fba36 100644
--- a/bon-sandbox/src/docs_in_private_items.rs
+++ b/bon-sandbox/src/docs_in_private_items.rs
@@ -11,6 +11,10 @@ struct ExampleStruct {
     #[builder(start_fn)]
     start_fn: u32,
 
+    /// Docs on `field` member
+    #[builder(field)]
+    field: u32,
+
     /// Docs on `finish_fn` member
     #[builder(finish_fn)]
     finish_fn: u32,
@@ -27,6 +31,10 @@ impl ExampleStruct {
         #[builder(start_fn)]
         start_fn: u32,
 
+        /// Docs on `field` member
+        #[builder(field)]
+        field: u32,
+
         /// Docs on `finish_fn` member
         #[builder(finish_fn)]
         finish_fn: u32,
@@ -35,6 +43,7 @@ impl ExampleStruct {
         regular: u32,
     ) {
         let _ = start_fn;
+        let _ = field;
         let _ = finish_fn;
         let _ = regular;
     }
@@ -47,6 +56,10 @@ impl ExampleStruct {
         #[builder(start_fn)]
         start_fn: u32,
 
+        /// Docs on `field` member
+        #[builder(field)]
+        field: u32,
+
         /// Docs on `finish_fn` member
         #[builder(finish_fn)]
         finish_fn: u32,
@@ -56,6 +69,7 @@ impl ExampleStruct {
     ) {
         let _ = self;
         let _ = start_fn;
+        let _ = field;
         let _ = finish_fn;
         let _ = regular;
     }
@@ -68,6 +82,10 @@ const fn example_function(
     #[builder(start_fn)]
     start_fn: u32,
 
+    /// Docs on `field` member
+    #[builder(field)]
+    field: u32,
+
     /// Docs on `finish_fn` member
     #[builder(finish_fn)]
     finish_fn: u32,
@@ -76,6 +94,7 @@ const fn example_function(
     regular: u32,
 ) {
     let _ = start_fn;
+    let _ = field;
     let _ = finish_fn;
     let _ = regular;
 }