diff --git a/trl/trainer/grpo_trainer.py b/trl/trainer/grpo_trainer.py
index ab83c8550a1..a9cfbf39a03 100644
--- a/trl/trainer/grpo_trainer.py
+++ b/trl/trainer/grpo_trainer.py
@@ -1292,7 +1292,7 @@ def _tokenize_prompts(self, prompts: list):
                 for message in prompt:
                     if isinstance(message["content"], list):
                         for part in message["content"]:
-                            if isinstance(part, dict) and part.get("type") == "image":
+                            if part["type"] == "image":
                                 prompt_images.append(part["image"])
                                 has_images = True
                 images.append(prompt_images if prompt_images else None)
@@ -1442,7 +1442,7 @@ def _get_tool_suffix_ids(self, tool_messages):
         for msg in tool_messages:
             if isinstance(msg.get("content"), list):
                 for part in msg["content"]:
-                    if isinstance(part, dict) and part.get("type") == "image":
+                    if part["type"] == "image":
                         tool_images.append(part["image"])
 
         # Normalize string content in tool messages for VLM processors before either path.
diff --git a/trl/trainer/rloo_trainer.py b/trl/trainer/rloo_trainer.py
index 67ed23ad65f..f9dd4280a5a 100644
--- a/trl/trainer/rloo_trainer.py
+++ b/trl/trainer/rloo_trainer.py
@@ -912,7 +912,7 @@ def _tokenize_prompts(self, prompts: list):
                 for message in prompt:
                     if isinstance(message["content"], list):
                         for part in message["content"]:
-                            if isinstance(part, dict) and part.get("type") == "image":
+                            if part["type"] == "image":
                                 prompt_images.append(part["image"])
                                 has_images = True
                 images.append(prompt_images if prompt_images else None)