diff --git a/doc/3.1-configuration-syntax.md b/doc/3.1-configuration-syntax.md
index 9493ecaf0..0c1163257 100644
--- a/doc/3.1-configuration-syntax.md
+++ b/doc/3.1-configuration-syntax.md
@@ -44,8 +44,8 @@ Example:
 
     2.5m
 
-Supported suffixes include ms (milliseconds), s (seconds), m (minutes)
-and h (hours).
+Supported suffixes include ms (milliseconds), s (seconds), m (minutes),
+h (hours) and d (days).
 
 #### String Literals