diff --git a/spec.md b/spec.md
index a26ea89..2c0ba7e 100644
--- a/spec.md
+++ b/spec.md
@@ -990,7 +990,9 @@ $i++;
 ++$j;
 ```
 
-Type casting operators MUST NOT have any space within the parentheses:
+Type casting operators MUST NOT have any space within the parentheses and MUST be separated from the variable they are
+operating on by exactly one space:
+
 ```php
 $intValue = (int) $input;
 ```