diff --git a/.github/workflows/test_rust.yml b/.github/workflows/test_rust.yml
index 29eef50ca5..ee86f6d64e 100644
--- a/.github/workflows/test_rust.yml
+++ b/.github/workflows/test_rust.yml
@@ -28,6 +28,5 @@ jobs:
           bazel-cache: rust_linux
           bazel: |
             test //rust:protobuf_upb_test //rust:protobuf_cpp_test \
-              //rust/upb_kernel:upb_test //rust/cpp_kernel:cpp_test \
               //rust/test/rust_proto_library_unit_test:rust_upb_aspect_test \
-              //rust/upb_kernel:upb_test //src/google/protobuf/compiler/rust/...
\ No newline at end of file
+              //src/google/protobuf/compiler/rust/...
\ No newline at end of file
diff --git a/rust/BUILD b/rust/BUILD
index e38f5644a2..6c2943d636 100644
--- a/rust/BUILD
+++ b/rust/BUILD
@@ -48,9 +48,17 @@ rust_library(
 # unittesting).
 rust_library(
     name = "protobuf_upb",
-    srcs = ["shared.rs"],
+    srcs = [
+        "shared.rs",
+        "upb.rs",
+    ],
+    crate_root = "shared.rs",
     rustc_flags = ["--cfg=upb_kernel"],
-    deps = ["//rust/upb_kernel:upb"],
+    visibility = [
+        "//src/google/protobuf:__subpackages__",
+        "//rust:__subpackages__",
+    ],
+    deps = ["//rust/upb_kernel:upb_c_api"],
 )
 
 rust_test(
@@ -72,9 +80,16 @@ rust_test(
 # See the comment for `:protobuf` for discussion of `shared.rs` file.
 rust_library(
     name = "protobuf_cpp",
-    srcs = ["shared.rs"],
+    srcs = [
+        "cpp.rs",
+        "shared.rs",
+    ],
+    crate_root = "shared.rs",
     rustc_flags = ["--cfg=cpp_kernel"],
-    deps = ["//rust/cpp_kernel:cpp"],
+    visibility = [
+        "//src/google/protobuf:__subpackages__",
+        "//rust:__subpackages__",
+    ],
 )
 
 rust_test(
diff --git a/rust/cpp_kernel/cpp.rs b/rust/cpp.rs
similarity index 95%
rename from rust/cpp_kernel/cpp.rs
rename to rust/cpp.rs
index 64e202b74e..835726627a 100644
--- a/rust/cpp_kernel/cpp.rs
+++ b/rust/cpp.rs
@@ -32,7 +32,6 @@
 
 use std::alloc;
 use std::alloc::Layout;
-use std::boxed::Box;
 use std::cell::UnsafeCell;
 use std::fmt;
 use std::marker::PhantomData;
@@ -51,6 +50,7 @@ use std::slice;
 ///
 /// Note that this type is neither `Sync` nor `Send`.
 pub struct Arena {
+    #[allow(dead_code)]
     ptr: NonNull<u8>,
     _not_sync: PhantomData<UnsafeCell<()>>,
 }
@@ -74,7 +74,7 @@ impl Arena {
     ///
     /// `layout`'s alignment must be less than `UPB_MALLOC_ALIGN`.
     #[inline]
-    pub unsafe fn alloc(&self, layout: Layout) -> &mut [MaybeUninit<u8>] {
+    pub unsafe fn alloc(&self, _layout: Layout) -> &mut [MaybeUninit<u8>] {
         unimplemented!()
     }
 
@@ -86,7 +86,7 @@ impl Arena {
     /// be the layout `ptr` was allocated with via [`Arena::alloc()`]. `new`'s
     /// alignment must be less than `UPB_MALLOC_ALIGN`.
     #[inline]
-    pub unsafe fn resize(&self, ptr: *mut u8, old: Layout, new: Layout) -> &[MaybeUninit<u8>] {
+    pub unsafe fn resize(&self, _ptr: *mut u8, _old: Layout, _new: Layout) -> &[MaybeUninit<u8>] {
         unimplemented!()
     }
 }
@@ -146,6 +146,7 @@ impl fmt::Debug for SerializedData {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::boxed::Box;
 
     // We need to allocate the byte array so SerializedData can own it and
     // deallocate it in its drop. This function makes it easier to do so for our
diff --git a/rust/cpp_kernel/BUILD b/rust/cpp_kernel/BUILD
index 3750498db5..0b9594b2e8 100644
--- a/rust/cpp_kernel/BUILD
+++ b/rust/cpp_kernel/BUILD
@@ -1,24 +1,6 @@
 # This package contains Rust protobuf runtime implementation built on top of the C++ backend.
 
-load("@rules_rust//rust:defs.bzl", "rust_library", "rust_test")
-
-rust_library(
-    name = "cpp",
-    srcs = ["cpp.rs"],
-    visibility = [
-        "//src/google/protobuf:__subpackages__",
-        "//rust:__subpackages__",
-    ],
-)
-
-rust_test(
-    name = "cpp_test",
-    crate = ":cpp",
-    tags = [
-        # TODO(b/270274576): Enable testing on arm once we have a Rust Arm toolchain.
-        "not_build:arm",
-    ],
-)
+load("@rules_rust//rust:defs.bzl", "rust_library")
 
 cc_library(
     name = "cpp_api",
@@ -36,4 +18,7 @@ cc_library(
 rust_library(
     name = "rust_alloc_for_cpp_api",
     srcs = ["rust_alloc_for_cpp_api.rs"],
+    visibility = [
+        "//rust:__subpackages__",
+    ],
 )
diff --git a/rust/shared.rs b/rust/shared.rs
index b576ca6929..e088660b6c 100644
--- a/rust/shared.rs
+++ b/rust/shared.rs
@@ -34,9 +34,11 @@
 //! crate.
 
 #[cfg(cpp_kernel)]
-pub extern crate cpp as __runtime;
+#[path = "cpp.rs"]
+pub mod __runtime;
 #[cfg(upb_kernel)]
-pub extern crate upb as __runtime;
+#[path = "upb.rs"]
+pub mod __runtime;
 
 pub use __runtime::SerializedData;
 
@@ -67,4 +69,4 @@ impl PtrAndLen {
     pub unsafe fn as_ref<'a>(self) -> &'a [u8] {
         slice::from_raw_parts(self.ptr, self.len)
     }
-}
\ No newline at end of file
+}
diff --git a/rust/upb_kernel/upb.rs b/rust/upb.rs
similarity index 100%
rename from rust/upb_kernel/upb.rs
rename to rust/upb.rs
diff --git a/rust/upb_kernel/BUILD b/rust/upb_kernel/BUILD
index 233c26024f..ecff4ce26f 100644
--- a/rust/upb_kernel/BUILD
+++ b/rust/upb_kernel/BUILD
@@ -1,29 +1,12 @@
 # This package contains Rust protobuf runtime implementation built on top of UPB.
 
-load("@rules_rust//rust:defs.bzl", "rust_library", "rust_test")
-
-rust_library(
-    name = "upb",
-    srcs = ["upb.rs"],
+cc_library(
+    name = "upb_c_api",
+    srcs = ["upb_api.c"],
     visibility = [
         "//src/google/protobuf:__subpackages__",
         "//rust:__subpackages__",
     ],
-    deps = [":upb_c_api"],
-)
-
-rust_test(
-    name = "upb_test",
-    crate = ":upb",
-    tags = [
-        # TODO(b/270274576): Enable testing on arm once we have a Rust Arm toolchain.
-        "not_build:arm",
-    ],
-)
-
-cc_library(
-    name = "upb_c_api",
-    srcs = ["upb_api.c"],
     deps = [
         "@upb//:upb",
     ],