diff --git a/source/reference/aggregation/substr.txt b/source/reference/aggregation/substr.txt
index dead4c8c9c7..4d59dd49ba0 100644
--- a/source/reference/aggregation/substr.txt
+++ b/source/reference/aggregation/substr.txt
@@ -13,6 +13,6 @@ $substr
 
    .. note::
 
-      ::expression:`$substr` is not encoding aware and if used
+      :expression:`$substr` is not encoding aware and if used
       improperly may produce a result string containing an invalid utf-8
       character sequence.