diff --git a/docs/voices.md b/docs/voices.md
index b264456f..6c4d72d5 100644
--- a/docs/voices.md
+++ b/docs/voices.md
@@ -28,6 +28,7 @@
   - [dictrules](#dictrules)
   - [lowercaseSentence](#lowercaseSentence)
   - [replace](#replace)
+  - [spellingStress](#spellingStress)
   - [stressOpt](#stressopt)
   - [stressRule](#stressrule)
   - [stressLength](#stresslength)
@@ -418,6 +419,12 @@ e.g.
 The phoneme mnemonics can be defined for each language, but some are
 listed in [Phonemes](phonemes.md).
 
+### spellingStress
+
+	spellingStress
+
+When set, stress first letter when reading abbreviations.
+
 ### stressOpt
 
 	stressOpt <list of rule numbers>