diff --git a/README.md b/README.md
index af25a27..64a877f 100644
--- a/README.md
+++ b/README.md
@@ -12,3 +12,9 @@ Use:
 >>> permanent(eye(15))
 (1-0j)
 ```
+Please note that the function assumes that the array contains complex numbers. So for example:
+```python
+>>> permanent(array([[0,1],[1,1]]), dtype=complex)
+(1+0j)
+```
+whereas using ```permanent(array([[0,1],[1,1]]))``` will not produce the expected result.