diff --git a/book/en/src/preface.md b/book/en/src/preface.md
index d8f64fd473..9bd6076bab 100644
--- a/book/en/src/preface.md
+++ b/book/en/src/preface.md
@@ -5,7 +5,8 @@
 # Preface
 
 This book contains user level documentation for the Real Time For the Masses
-(RTFM) framework. The API reference can be found [here](../api/rtfm/index.html).
+(RTFM) framework. The API reference can be found
+[here](../../api/rtfm/index.html).
 
 There is a translation of this book in [Russian].