diff --git a/modules/chat.py b/modules/chat.py
index 1a16a689..c10d91a7 100644
--- a/modules/chat.py
+++ b/modules/chat.py
@@ -108,7 +108,14 @@ def get_generation_prompt(renderer, impersonate=False, strip_trailing_spaces=Tru
 
     suffix_plus_prefix = prompt.split("<<|user-message-1|>>")[1].split("<<|user-message-2|>>")[0]
     suffix = prompt.split("<<|user-message-2|>>")[1]
-    prefix = suffix_plus_prefix[len(suffix):]
+
+    # Remove the message suffix. The first case handles the GPT-OSS model
+    # in a way that is likely to not interfere with previous models.
+    if '<|start|>user' in suffix_plus_prefix or '<|start|>assistant' in suffix_plus_prefix:
+        start_index = suffix_plus_prefix.rindex('<|start|>')
+        prefix = suffix_plus_prefix[start_index:]
+    else:
+        prefix = suffix_plus_prefix[len(suffix):]
 
     if strip_trailing_spaces:
         prefix = prefix.rstrip(' ')