diff --git a/transform.Rmd b/transform.Rmd
index 8af7dd1..acb2c8b 100644
--- a/transform.Rmd
+++ b/transform.Rmd
@@ -125,7 +125,7 @@ The following code finds all flights that departed in November or December:
 filter(flights, month == 11 | month == 12)
 ```
 
-The order of operations doesn't work like English. You can't write `filter(flights, month == 11 | 12)`, which you might literally translate into  "finds all flights that departed in November or December". Instead it finds all months that equal `11 | 12`, an expression that evaluates to `TRUE`. In a numeric context (like here), `TRUE` becomes one, so this finds all flights in January, not November or December. This is quite confusing!
+The order of operations doesn't work like English. You can't write `filter(flights, month == (11 | 12))`, which you might literally translate into  "finds all flights that departed in November or December". Instead it finds all months that equal `11 | 12`, an expression that evaluates to `TRUE`. In a numeric context (like here), `TRUE` becomes one, so this finds all flights in January, not November or December. This is quite confusing!
 
 A useful short-hand for this problem is `x %in% y`. This will select every row where `x` is one of the values in `y`. We could use it to rewrite the code above: