diff --git a/tests/resources/ATAN2.xlsx b/tests/resources/ATAN2.xlsx
old mode 100644
new mode 100755
index 10665bc..6ca228f
Binary files a/tests/resources/ATAN2.xlsx and b/tests/resources/ATAN2.xlsx differ
diff --git a/tests/xlfunctions/test_math.py b/tests/xlfunctions/test_math.py
index 87838a1..e0d44ad 100644
--- a/tests/xlfunctions/test_math.py
+++ b/tests/xlfunctions/test_math.py
@@ -41,6 +41,7 @@ def test_ATAN(self):
     def test_ARTAN2(self):
         self.assertAlmostEqual(math.ATAN2(1, 1), 0.785398163)
         self.assertAlmostEqual(math.ATAN2(-1, -1), -2.35619449)
+        self.assertAlmostEqual(math.ATAN2(1, 2), 1.10714872)
 
     def test_CEILING_number(self):
         self.assertEqual(math.CEILING(2.5, 1), 3)
diff --git a/tests/xlfunctions_vs_excel/atan2_test.py b/tests/xlfunctions_vs_excel/atan2_test.py
index e85dcc3..4c328f8 100644
--- a/tests/xlfunctions_vs_excel/atan2_test.py
+++ b/tests/xlfunctions_vs_excel/atan2_test.py
@@ -28,3 +28,9 @@ def test_evaluation_A5(self):
             self.evaluator.evaluate('Sheet1!A5'),
             self.evaluator.get_cell_value('Sheet1!A5')
         )
+
+    def test_evaluation_A6(self):
+        self.assertEqual(
+            self.evaluator.evaluate('Sheet1!A6'),
+            self.evaluator.get_cell_value('Sheet1!A6')
+        )
diff --git a/xlcalculator/xlfunctions/math.py b/xlcalculator/xlfunctions/math.py
index f167fe8..621138f 100644
--- a/xlcalculator/xlfunctions/math.py
+++ b/xlcalculator/xlfunctions/math.py
@@ -111,7 +111,7 @@ def ATAN2(
     https://support.office.com/en-us/article/
         atan2-function-c04592ab-b9e3-4908-b428-c96b3a565033
     """
-    return np.arctan2(float(x_num), float(y_num))
+    return np.arctan2(float(y_num), float(x_num))
 
 
 @xl.register()