diff --git a/meta/classes-recipe/ptest-cargo.bbclass b/meta/classes-recipe/ptest-cargo.bbclass
index 62444e9cc6..5cdd1c43d1 100644
--- a/meta/classes-recipe/ptest-cargo.bbclass
+++ b/meta/classes-recipe/ptest-cargo.bbclass
@@ -5,39 +5,28 @@ RUST_TEST_ARGS[doc] = "Arguments to give to the test binaries (e.g. --shuffle)"
 
 # I didn't find a cleaner way to share data between compile and install tasks
 CARGO_TEST_BINARIES_FILES ?= "${B}/test_binaries_list"
+CARGO_TEST_BUILD_JSON ?= "${B}/cargo_test_build.json"
+
+# Build the tests with the same environment as do_compile (oe_cargo_fix_env).
+cargo_ptest_build () {
+    oe_cargo_fix_env
+    export RUSTFLAGS="${RUSTFLAGS}"
+    bbnote "Building tests with cargo"
+    "${CARGO}" build --tests --message-format json-render-diagnostics ${CARGO_BUILD_FLAGS} ${PACKAGECONFIG_CONFARGS} > "${CARGO_TEST_BUILD_JSON}"
+}
 
 # Sadly, generated test binaries have no deterministic names (https://github.com/rust-lang/cargo/issues/1924)
 # This forces us to parse the cargo output in json format to find those test binaries.
 python do_compile_ptest_cargo() {
-    import subprocess
     import json
 
-    cargo = bb.utils.which(d.getVar("PATH"), d.getVar("CARGO"))
-    cargo_build_flags = d.getVar("CARGO_BUILD_FLAGS")
-    packageconfig_confargs = d.getVar("PACKAGECONFIG_CONFARGS")
-    rust_flags = d.getVar("RUSTFLAGS")
     manifest_path = d.getVar("CARGO_MANIFEST_PATH")
     project_manifest_path = os.path.normpath(manifest_path)
     manifest_dir = os.path.dirname(manifest_path)
 
-    env = os.environ.copy()
-    env['RUSTFLAGS'] = rust_flags
-    cmd = f"{cargo} build --tests --message-format json {cargo_build_flags} {packageconfig_confargs}"
-    bb.note(f"Building tests with cargo ({cmd})")
-
-    try:
-        proc = subprocess.Popen(cmd, shell=True, env=env, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, text=True)
-    except subprocess.CalledProcessError as e:
-        bb.fatal(f"Cannot build test with cargo: {e}")
-
-    lines = []
-    for line in proc.stdout:
-        data = line.strip('\n')
-        lines.append(data)
-        bb.note(data)
-    proc.communicate()
-    if proc.returncode != 0:
-        bb.fatal(f"Unable to compile test with cargo, '{cmd}' failed")
+    bb.build.exec_func("cargo_ptest_build", d)
+    with open(d.getVar("CARGO_TEST_BUILD_JSON")) as f:
+        lines = f.read().splitlines()
 
     # Definition of the format: https://doc.rust-lang.org/cargo/reference/external-tools.html#json-messages
     test_bins = []