diff --git a/doc/api.md b/doc/api.md
index 2e3de9a..9725004 100644
--- a/doc/api.md
+++ b/doc/api.md
@@ -13,7 +13,7 @@ Import necessary modules:
 Create a KmerCountTable with a k-mer size of 31:
 
 ```python
->>> counts = oxli.KmerCountTable(31)
+>>> counts = oxli.KmerCountTable(ksize=31)
 
 ```
 
diff --git a/src/lib.rs b/src/lib.rs
index 4f2164b..61b1444 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -19,6 +19,7 @@ struct KmerCountTable {
 #[pymethods]
 impl KmerCountTable {
     #[new]
+    #[pyo3(signature = (ksize))]
     pub fn new(ksize: u8) -> Self {
         Self {
             counts: HashMap::new(),