diff --git a/test-cargo-miri/Cargo.lock b/test-cargo-miri/Cargo.lock
index 3f61fb3d540..38bfb2ac620 100644
--- a/test-cargo-miri/Cargo.lock
+++ b/test-cargo-miri/Cargo.lock
@@ -48,15 +48,6 @@ dependencies = [
 name = "exported_symbol_dep"
 version = "0.1.0"
 
-[[package]]
-name = "hermit-abi"
-version = "0.1.19"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "62b467343b94ba476dcb2500d242dadbb39557df889310ac77c5d99100aaac33"
-dependencies = [
- "libc",
-]
-
 [[package]]
 name = "issue_1567"
 version = "0.1.0"
@@ -83,22 +74,6 @@ version = "0.1.0"
 name = "issue_rust_86261"
 version = "0.1.0"
 
-[[package]]
-name = "libc"
-version = "0.2.126"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "349d5a591cd28b49e1d1037471617a32ddcda5731b99419008085f72d5a53836"
-
-[[package]]
-name = "num_cpus"
-version = "1.13.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "19e64526ebdee182341572e50e9ad03965aa510cd94427a4549448f285e957a1"
-dependencies = [
- "hermit-abi",
- "libc",
-]
-
 [[package]]
 name = "proc-macro2"
 version = "1.0.40"
@@ -132,7 +107,7 @@ dependencies = [
 name = "subcrate"
 version = "0.1.0"
 dependencies = [
- "num_cpus",
+ "byteorder 1.4.3",
 ]
 
 [[package]]
diff --git a/test-cargo-miri/subcrate/Cargo.toml b/test-cargo-miri/subcrate/Cargo.toml
index ea2936d52a0..06b1ce1cba4 100644
--- a/test-cargo-miri/subcrate/Cargo.toml
+++ b/test-cargo-miri/subcrate/Cargo.toml
@@ -18,4 +18,4 @@ path = "test.rs"
 harness = false
 
 [dev-dependencies]
-num_cpus = "1.10.1"
+byteorder = "1.0"
diff --git a/test-cargo-miri/subcrate/test.rs b/test-cargo-miri/subcrate/test.rs
index fdab9402813..77e3c2878ca 100644
--- a/test-cargo-miri/subcrate/test.rs
+++ b/test-cargo-miri/subcrate/test.rs
@@ -1,5 +1,7 @@
 use std::env;
 
+use byteorder::{ByteOrder, LittleEndian};
+
 fn main() {
     println!("subcrate testing");
 
@@ -11,6 +13,6 @@ fn main() {
     let crate_dir = crate_dir.to_string_lossy().replace("\\", "/");
     assert_eq!(env_dir, crate_dir);
 
-    // Make sure we can call `num_cpus`.
-    num_cpus::get();
+    // Make sure we can call dev-dependencies.
+    let _n = <LittleEndian as ByteOrder>::read_u32(&[1, 2, 3, 4]);
 }