diff --git a/measprocess/preprocess.py b/measprocess/preprocess.py
index 63044e971e2fd4c32791293340a99f6e28951c22..a6864f581966de4164d8488e361657aa5e12ae8a 100644
--- a/measprocess/preprocess.py
+++ b/measprocess/preprocess.py
@@ -3,7 +3,7 @@ import itertools
 import numpy as np
 from tqdm import tqdm
 
-def link_dataframes(A: pd.DataFrame, B: pd.DataFrame, ref_col: str, metric=None, verbose=True) -> (pd.DataFrame, np.array):
+def link_dataframes(A: pd.DataFrame, B: pd.DataFrame, ref_col: str, metric=None, verbose=True) -> (pd.DataFrame, np.ndarray):
     '''
     Merge two DataFrames A and B according to the reference colum based on minimum metric.
 
diff --git a/setup.py b/setup.py
index 86a234f654f10c9ec7cf9f114b934efa1211f2c6..52a17690b653fff6bed1c30265f336ba299fe78a 100644
--- a/setup.py
+++ b/setup.py
@@ -10,7 +10,7 @@ README = (HERE / "README.md").read_text()
 # This call to setup() does all the work
 setup(
     name="measprocess",
-    version="0.5.6",
+    version="0.5.9",
     description="Collection of measurement processing tools",
     long_description=README,
     long_description_content_type="text/markdown",