diff --git a/ch04_keys.adoc b/ch04_keys.adoc
index 5439fb7e..a3ccf953 100644
--- a/ch04_keys.adoc
+++ b/ch04_keys.adoc
@@ -170,7 +170,7 @@ curve.
 by Bitcoin.
 
 [[ecc-curve]]
-[role="width-40"]
+[role="width-30"]
 .An elliptic curve
 image::images/mbc3_0402.png["ecc-curve"]