diff --git a/wagtail/search/backends/elasticsearch2.py b/wagtail/search/backends/elasticsearch2.py
index e8b19a4c1..7b55ccdc3 100644
--- a/wagtail/search/backends/elasticsearch2.py
+++ b/wagtail/search/backends/elasticsearch2.py
@@ -464,7 +464,7 @@ class Elasticsearch2SearchQueryCompiler(BaseSearchQueryCompiler):
             }
 
         elif isinstance(query, PlainText):
-            return self._compile_plaintext_query(self.query, [field], boost)
+            return self._compile_plaintext_query(query, [field], boost)
 
 
         elif isinstance(query, Boost):