diff --git a/tools/push3-evolution/evolve.sh b/tools/push3-evolution/evolve.sh
index 4448c4d..c883aae 100755
--- a/tools/push3-evolution/evolve.sh
+++ b/tools/push3-evolution/evolve.sh
@@ -462,9 +462,15 @@ for gen in $(seq 0 $((GENERATIONS - 1))); do
 
     if [ "${#_BATCH_FILES[@]}" -gt 0 ]; then
       BATCH_EC=0
-      bash "$BATCH_EVAL_SH" "${_BATCH_FILES[@]}" > "$BATCH_SCORES_FILE" 2>/dev/null \
+      bash "$BATCH_EVAL_SH" "${_BATCH_FILES[@]}" > "$BATCH_SCORES_FILE" 2>"${TMPDIR}/batch-eval.log" \
         || BATCH_EC=$?
 
+      if [ "$BATCH_EC" -ne 0 ]; then
+        echo "--- last 20 lines of ${TMPDIR}/batch-eval.log ---" >&2
+        tail -n 20 "${TMPDIR}/batch-eval.log" >&2
+        echo "--- end batch-eval.log ---" >&2
+      fi
+
       if [ "$BATCH_EC" -eq 2 ]; then
         fail "batch-eval.sh reported an infrastructure error (exit 2) — aborting evolution"
       fi