diff --git a/python/ycm/completers/completer.py b/python/ycm/completers/completer.py
index 60dcd6ec..6e2f1486 100644
--- a/python/ycm/completers/completer.py
+++ b/python/ycm/completers/completer.py
@@ -19,6 +19,7 @@
 
 import abc
 import ycm_core
+from ycm.utils import ToUtf8IfNeeded
 from ycm.completers.completer_utils import TriggersForFiletype
 
 NO_USER_COMMANDS = 'This completer does not define any commands.'
@@ -177,7 +178,7 @@ class Completer( object ):
       self.completions_cache.filtered_completions = (
         self.FilterAndSortCandidates(
           self.completions_cache.raw_completions,
-          request_data[ 'query' ] ) )
+          ToUtf8IfNeeded( request_data[ 'query' ] ) ) )
     else:
       self.completions_cache = None
       self.CandidatesForQueryAsyncInner( request_data )
diff --git a/python/ycm/completers/cpp/clang_completer.py b/python/ycm/completers/cpp/clang_completer.py
index fc976ab1..73e90eef 100644
--- a/python/ycm/completers/cpp/clang_completer.py
+++ b/python/ycm/completers/cpp/clang_completer.py
@@ -22,6 +22,7 @@ import ycm_core
 import logging
 from ycm import server_responses
 from ycm import extra_conf_store
+from ycm.utils import ToUtf8IfNeeded
 from ycm.completers.completer import Completer
 from ycm.completers.cpp.flags import Flags
 
@@ -109,8 +110,8 @@ class ClangCompleter( Completer ):
     column = request_data[ 'start_column' ] + 1
     self.completions_future = (
       self.completer.CandidatesForQueryAndLocationInFileAsync(
-        query,
-        filename,
+        ToUtf8IfNeeded( query ),
+        ToUtf8IfNeeded( filename ),
         line,
         column,
         files,
@@ -369,3 +370,5 @@ def ClangAvailableForFiletypes( filetypes ):
 
 def InCFamilyFile( filetypes ):
   return ClangAvailableForFiletypes( filetypes )
+
+
diff --git a/python/ycm/utils.py b/python/ycm/utils.py
index d1fe5035..81e4bd77 100644
--- a/python/ycm/utils.py
+++ b/python/ycm/utils.py
@@ -24,3 +24,8 @@ def IsIdentifierChar( char ):
 def SanitizeQuery( query ):
   return query.strip()
 
+
+def ToUtf8IfNeeded( string_or_unicode ):
+  if isinstance( string_or_unicode, unicode ):
+    return string_or_unicode.encode( 'utf8' )
+  return string_or_unicode