diff --git a/openapi_core/contrib/aiohttp/responses.py b/openapi_core/contrib/aiohttp/responses.py
index 40771e2f..a7baf851 100644
--- a/openapi_core/contrib/aiohttp/responses.py
+++ b/openapi_core/contrib/aiohttp/responses.py
@@ -17,7 +17,10 @@ def data(self) -> str:
         if self.response.body is None:
             return ""
         if isinstance(self.response.body, bytes):
-            return self.response.body.decode("utf-8")
+            try:
+                return self.response.body.decode("utf-8")
+            except UnicodeDecodeError:
+                return self.response.body
         assert isinstance(self.response.body, str)
         return self.response.body