diff --git a/doc/src/manual/performance-tips.md b/doc/src/manual/performance-tips.md
index b830f34a07b1d..ce86bc9ffdf9a 100644
--- a/doc/src/manual/performance-tips.md
+++ b/doc/src/manual/performance-tips.md
@@ -1231,7 +1231,7 @@ function mynorm(u::Vector)
     @fastmath @inbounds @simd for i in 1:n
         s += u[i]^2
     end
-    @fastmath @inbounds return sqrt(s/n)
+    @fastmath @inbounds return sqrt(s)
 end
 
 function main()