diff --git a/ch04.r b/ch04.r
index de58f57..6340d7a 100644
--- a/ch04.r
+++ b/ch04.r
@@ -118,5 +118,5 @@ X1 = runif(N, 1, 6)
 X2 = runif(N, 1, 6)
 X3 = runif(N, 1, 6)
 Z = X1 + X2 + X3
-hist(Z, breaks=seq(2.5,17.5))
+hist(Z, breaks=seq(2.5,18.5))