diff --git a/netmiko/ciena/ciena_saos.py b/netmiko/ciena/ciena_saos.py
index f3c0c21ee..b74a61c64 100644
--- a/netmiko/ciena/ciena_saos.py
+++ b/netmiko/ciena/ciena_saos.py
@@ -28,7 +28,7 @@ def set_base_prompt(
         prompt = self.find_prompt(delay_factor=delay_factor)
 
         pattern = rf"^.+{self.prompt_pattern}$"
-        if re.search(pattern, prompt):
+        if not re.search(pattern, prompt):
             raise ValueError(f"Router prompt not found: {repr(prompt)}")
         # Strip off trailing terminator
         self.base_prompt = prompt[:-1]