diff --git a/doc/CustomizingEigen_CustomScalar.dox b/doc/CustomizingEigen_CustomScalar.dox
index 1ee78cb..24e5f56 100644
--- a/doc/CustomizingEigen_CustomScalar.dox
+++ b/doc/CustomizingEigen_CustomScalar.dox
@@ -75,7 +75,7 @@
 
     static inline Real epsilon() { return 0; }
     static inline Real dummy_precision() { return 0; }
-    static inline Real digits10() { return 0; }
+    static inline int digits10() { return 0; }
 
     enum {
       IsInteger = 0,