diff --git a/vcsserver/base.py b/vcsserver/base.py
--- a/vcsserver/base.py
+++ b/vcsserver/base.py
@@ -187,7 +187,7 @@ class BytesEnvelope(bytes):
         if isinstance(content, bytes):
             return super().__new__(cls, content)
         else:
-            raise TypeError('Content must be bytes.')
+            raise TypeError('BytesEnvelope content= param must be bytes. Use BinaryEnvelope to wrap other types')
 
 
 class BinaryBytesEnvelope(BytesEnvelope):
diff --git a/vcsserver/remote/git.py b/vcsserver/remote/git.py
--- a/vcsserver/remote/git.py
+++ b/vcsserver/remote/git.py
@@ -1307,7 +1307,7 @@ class GitRemote(RemoteBase):
 
                 result_libgit.append((line_no, blame_commit_id, line))
 
-        return result_libgit
+        return BinaryEnvelope(result_libgit)
 
     @reraise_safe_exceptions
     def update_server_info(self, wire):
diff --git a/vcsserver/remote/hg.py b/vcsserver/remote/hg.py
--- a/vcsserver/remote/hg.py
+++ b/vcsserver/remote/hg.py
@@ -598,8 +598,8 @@ class HgRemote(RemoteBase):
             ln_no = i
             sha = hex(annotate_obj.fctx.node())
             content = annotate_obj.text
-            result.append((ln_no, sha, content))
-        return result
+            result.append((ln_no, ascii_str(sha), content))
+        return BinaryEnvelope(result)
 
     @reraise_safe_exceptions
     def fctx_node_data(self, wire, revision, path):
diff --git a/vcsserver/remote/svn.py b/vcsserver/remote/svn.py
--- a/vcsserver/remote/svn.py
+++ b/vcsserver/remote/svn.py
@@ -344,10 +344,10 @@ class SvnRemote(RemoteBase):
         except svn.core.SubversionException as exc:
             log.exception("Error during blame operation.")
             raise Exception(
-                "Blame not supported or file does not exist at path %s. "
-                "Error %s." % (path, exc))
+                f"Blame not supported or file does not exist at path {path}. "
+                f"Error {exc}.")
 
-        return annotations
+        return BinaryEnvelope(annotations)
 
     @reraise_safe_exceptions
     def get_node_type(self, wire, revision=None, path=''):