diff --git a/src/control-flow/if-expressions.md b/src/control-flow/if-expressions.md
index 4afa2371..1c7d86ed 100644
--- a/src/control-flow/if-expressions.md
+++ b/src/control-flow/if-expressions.md
@@ -25,3 +25,9 @@ fn main() {
     };
 }
 ```
+
+<details>
+
+Because `if` is an expression and must have a particular type, both of its branch blocks must have the same type. Consider showing what happens if you add `;` after `x / 2` in the second example.
+    
+</details>