diff --git a/tools/test_linux_port.py b/tools/test_linux_port.py
index 6ccdacd6..4793a0b2 100644
--- a/tools/test_linux_port.py
+++ b/tools/test_linux_port.py
@@ -314,7 +314,10 @@ def test_p2p_signatures_and_listings(tmp_path):
         pytest.skip("needs clang, ninja and a configured build")
     command = subprocess.run(["ninja", "-t", "commands", "build/linux/obj/port/linux/src/p2p_crypto.o"],
                              capture_output=True, text=True, check=True).stdout.strip().splitlines()[-1]
-    words = shlex.split(command)[1:]
+    words = shlex.split(command)
+    # (the compiler, and whatever runs it, ccache in CI: up to the first flag)
+    while words and not words[0].startswith("-"):
+        words = words[1:]
     flags = []
     skip = False
     for word in words:
@@ -327,10 +330,12 @@ def test_p2p_signatures_and_listings(tmp_path):
         else:
             flags.append(word)
     program = tmp_path / "p2p_lobby_check"
-    subprocess.run(["clang", *flags, "-O1", "-no-pie", "-Wl,--unresolved-symbols=ignore-all", "-o", str(program),
-                    "tools/p2p_lobby_check.c", "port/linux/src/p2p_crypto.c", "port/linux/src/p2p_lobby.c",
-                    "port/third_party/monocypher/monocypher.c", "port/third_party/monocypher/monocypher-ed25519.c"],
-                   check=True, capture_output=True)
+    built = subprocess.run(["clang", *flags, "-O1", "-no-pie", "-Wl,--unresolved-symbols=ignore-all", "-o",
+                            str(program), "tools/p2p_lobby_check.c", "port/linux/src/p2p_crypto.c",
+                            "port/linux/src/p2p_lobby.c", "port/third_party/monocypher/monocypher.c",
+                            "port/third_party/monocypher/monocypher-ed25519.c"],
+                           capture_output=True, text=True)
+    assert built.returncode == 0, built.stderr[-4000:]
     result = subprocess.run([str(program)], capture_output=True, text=True, timeout=60)
     assert result.returncode == 0, result.stdout
     assert "PASS" in result.stdout