diff --git a/scripts/copr-build.sh b/scripts/copr-build.sh
index 7d15fea..db8542c 100755
--- a/scripts/copr-build.sh
+++ b/scripts/copr-build.sh
@@ -39,14 +39,24 @@ build_state() {
 # terminal state, or "unknown" if we ran out of patience.
 wait_for_terminal_state() {
   local build_id="$1"
-  local deadline=$(($(date +%s) + BUILD_TIMEOUT))
-  local state
+  local started deadline state now
+  started=$(date +%s)
+  deadline=$((started + BUILD_TIMEOUT))
   state="$(build_state "$build_id")"
   while ! is_terminal_state "$state"; do
-    if [ "$(date +%s)" -ge "$deadline" ]; then
+    now=$(date +%s)
+    if [ "$now" -ge "$deadline" ]; then
       echo "unknown"
       return
     fi
+    # Heartbeat on stderr (stdout carries the return value). A COPR build emits
+    # nothing between state transitions, so a long build leaves the step silent
+    # for its whole duration — and a silent step gets killed by the runner's
+    # inactivity timeout before it can finish. Two builds died this way after
+    # ~24-27 minutes of no output, one of them 66 seconds before COPR reported
+    # success. Printing every poll keeps the step alive and shows progress.
+    printf '  [%3dm %3ds] build %s: %s\n' \
+      $(((now - started) / 60)) $(((now - started) % 60)) "$build_id" "${state:-unknown}" >&2
     sleep "$POLL_INTERVAL"
     state="$(build_state "$build_id")"
   done
diff --git a/tests/test-copr-build.sh b/tests/test-copr-build.sh
index a364fd5..f2dfdb8 100755
--- a/tests/test-copr-build.sh
+++ b/tests/test-copr-build.sh
@@ -92,6 +92,11 @@ run_case "canceled build exits 1" \
 run_case "skipped build exits 0" \
   0 "was skipped" STUB_WATCH_HANGS=0 STUB_STATES="skipped"
 
+# A build that takes a while must keep producing output, or the runner's
+# inactivity timeout kills the step before COPR finishes.
+CASE_TIMEOUT=6 run_case "slow build emits a heartbeat while waiting" \
+  0 "build 12345: running" STUB_WATCH_HANGS=1 STUB_STATES="running running running succeeded"
+
 # Never settles: bounded, and reported as a timeout rather than a build failure.
 CASE_TIMEOUT=3 run_case "build that never settles times out" \
   1 "gave up after" STUB_WATCH_HANGS=1 STUB_STATES="running"