diff --git a/openwakeword/custom_verifier_model.py b/openwakeword/custom_verifier_model.py
index e6c07d1..8846624 100644
--- a/openwakeword/custom_verifier_model.py
+++ b/openwakeword/custom_verifier_model.py
@@ -152,9 +152,9 @@ def train_custom_verifier(
          for i in tqdm(positive_reference_clips, desc="Processing positive reference clips")]
     )
     if positive_features.shape[0] == 0:
-        raise ValueError("The positive features were created! Make sure that"
+        raise ValueError("The positive features were not created! Make sure that"
                          " the positive reference clips contain the appropriate audio"
-                         " for the desired model")
+                         " for the desired model.")
 
     # Get features from negative reference clips
     negative_features = np.vstack(