diff --git a/moto/s3/responses.py b/moto/s3/responses.py
index 9cc94ca03..954bf6706 100644
--- a/moto/s3/responses.py
+++ b/moto/s3/responses.py
@@ -233,6 +233,8 @@ class ResponseObject(_TemplateEnvironmentMixin):
 
         bucket = self.backend.get_bucket(bucket_name)
         prefix = querystring.get('prefix', [None])[0]
+        if prefix:
+            prefix = prefix.decode("utf-8")
         delimiter = querystring.get('delimiter', [None])[0]
         result_keys, result_folders = self.backend.prefix_query(
             bucket, prefix, delimiter)
@@ -250,6 +252,8 @@ class ResponseObject(_TemplateEnvironmentMixin):
         bucket = self.backend.get_bucket(bucket_name)
 
         prefix = querystring.get('prefix', [None])[0]
+        if prefix:
+            prefix = prefix.decode("utf-8")
         delimiter = querystring.get('delimiter', [None])[0]
         result_keys, result_folders = self.backend.prefix_query(
             bucket, prefix, delimiter)
@@ -278,7 +282,7 @@ class ResponseObject(_TemplateEnvironmentMixin):
 
         return template.render(
             bucket=bucket,
-            prefix=prefix or '',
+            prefix=prefix or b'',
             delimiter=delimiter,
             result_keys=result_keys,
             result_folders=result_folders,