diff --git a/lassie/images/phase_net.py b/lassie/images/phase_net.py
index 602f4b11..5fb108b7 100644
--- a/lassie/images/phase_net.py
+++ b/lassie/images/phase_net.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import asyncio
 import logging
 from datetime import datetime, timedelta
 from typing import TYPE_CHECKING, Any, Literal
@@ -162,7 +163,8 @@ async def process_traces(self, traces: list[Trace]) -> list[PhaseNetImage]:
             for tr in stream:
                 tr.stats.sampling_rate = tr.stats.sampling_rate / scale
 
-        annotations: Stream = self._phase_net.annotate(
+        annotations: Stream = await asyncio.to_thread(
+            self._phase_net.annotate,
             stream,
             overlap=self.window_overlap_samples,
             batch_size=self.batch_size