diff --git a/trl/trainer/utils.py b/trl/trainer/utils.py
index 564dd3699be..577194db279 100644
--- a/trl/trainer/utils.py
+++ b/trl/trainer/utils.py
@@ -775,7 +775,7 @@ def format_entry(entry) -> Text:
                         t.append(reasoning, style="italic dim white")
                         t.append("\n")
                     if "content" in msg:
-                        t.append(msg["content"])
+                        t.append(msg["content"] or "")
                 elif "name" in msg and "args" in msg:
                     # Tool call
                     t.append(f"{role.upper()}\n", style="bold red")