diff --git a/batbot/__init__.py b/batbot/__init__.py
index 585ce0a..a432684 100644
--- a/batbot/__init__.py
+++ b/batbot/__init__.py
@@ -33,7 +33,7 @@
 
 from batbot import spectrogram  # NOQA
 
-VERSION = '0.1.3'
+VERSION = '0.1.4'
 version = VERSION
 __version__ = VERSION
 
diff --git a/batbot/spectrogram/__init__.py b/batbot/spectrogram/__init__.py
index bf51efb..255c1fa 100644
--- a/batbot/spectrogram/__init__.py
+++ b/batbot/spectrogram/__init__.py
@@ -1114,9 +1114,11 @@ def extract_contour_keypoints(
             'slope/mid[avg].y_px/x_px': float(np.mean(der1[knee_idx : heel_idx + 1])),
             'slope/lo[avg].y_px/x_px': float(np.mean(der1[heel_idx:])),
             'slope[box].y_px/x_px': -float((y_[-1] - y_[0]) / (x_[-1] - x_[0] + 1e-10)),
-            'slope/hi[box].y_px/x_px': -float((y_[fc_idx] - y_[0]) / (x_[fc_idx] - x_[0] + 1e-10)),
+            'slope/hi[box].y_px/x_px': -float(
+                (y_[knee_idx] - y_[0]) / (x_[knee_idx] - x_[0] + 1e-10)
+            ),
             'slope/lo[box].y_px/x_px': -float(
-                (y_[-1] - y_[fc_idx]) / (x_[-1] - x_[fc_idx] + 1e-10)
+                (y_[fc_idx] - y_[knee_idx]) / (x_[fc_idx] - x_[knee_idx] + 1e-10)
             ),
         }