diff --git a/resultsdb.py b/resultsdb.py
index e709038..03d2299 100644
--- a/resultsdb.py
+++ b/resultsdb.py
@@ -78,6 +78,30 @@
 # Jenkins sets LIBTEST_DB once for the whole pipeline rather than passing --db
 # to every script invocation.
 DEFAULT_DB = os.environ.get("LIBTEST_DB") or "sqlite3.db"
+
+
+def hostname():
+  """The machine the testing is running on, as something a human recognises.
+
+  socket.gethostname() is that machine, right up until the run is inside a
+  container, where it is the container id instead: job_claim holds rows saying
+  the wasm-jit libraries were tested by "e9725d308091", which identifies nothing
+  and is gone with the container. Jenkins does know the machine - it names its
+  agents - and propagates NODE_NAME into a container it starts, so prefer that
+  when there is a container to see through. LIBTEST_HOST overrides both, for
+  the same reason LIBTEST_DB exists.
+
+  Only consulted inside a container: outside one the kernel's answer is the
+  right one, and a NODE_NAME left over in the environment should not override
+  it.
+  """
+  explicit = os.environ.get("LIBTEST_HOST")
+  if explicit:
+    return explicit
+  # Docker leaves /.dockerenv behind, podman /run/.containerenv.
+  if os.path.exists("/.dockerenv") or os.path.exists("/run/.containerenv"):
+    return os.environ.get("NODE_NAME") or socket.gethostname()
+  return socket.gethostname()
 DB_HELP = ("Result database: a local sqlite3 file, or a postgresql://user@host/database URL for "
            "the shared one, taken from the LIBTEST_DB environment variable when not given. "
            "Several machines can write to the shared database at the same time; a library "
@@ -304,7 +328,7 @@ def __init__(self, url):
     self.lostConnection = (psycopg2.OperationalError, psycopg2.InterfaceError)
     self.pending = []
     self.conn = self._connect()
-    self.host = socket.gethostname()
+    self.host = hostname()
     self.claims = []
     self.heartbeatThread = None
     self.execute(JOB_CLAIM)
diff --git a/test.py b/test.py
index 8351f66..6cb7797 100755
--- a/test.py
+++ b/test.py
@@ -12,7 +12,6 @@
 from joblib import Parallel, delayed
 import simplejson as json
 import psutil, subprocess, threading, hashlib
-import socket
 from subprocess import call
 from monotonic import monotonic
 from omcommon import friendlyStr, multiple_replace
@@ -1011,7 +1010,7 @@ def cpu_name():
   except:
     lsb_release = ""
 
-hostname = socket.gethostname()
+hostname = resultsdb.hostname()
 sysInfo = "%s: %s, %d GB RAM, %s%s" % (hostname, cpu_name(), int(math.ceil(psutil.virtual_memory().total / (1024.0**3))), ("Docker " + docker + " ") if docker else "", lsb_release)
 
 for (resultBranch, simulator) in resultBranches: