diff --git a/util/flags.py b/util/flags.py
index 624217e0..dda3cd58 100644
--- a/util/flags.py
+++ b/util/flags.py
@@ -15,7 +15,7 @@ def create_flags():
     f.DEFINE_string('dev_files', '', 'comma separated list of files specifying the dataset used for validation. Multiple files will get merged. If empty, validation will not be run.')
     f.DEFINE_string('test_files', '', 'comma separated list of files specifying the dataset used for testing. Multiple files will get merged. If empty, the model will not be tested.')
 
-    f.DEFINE_string('feature_cache', '', 'path where cached features extracted from --train_files will be saved. If empty, caching will be done in memory and no files will be written.')
+    f.DEFINE_string('feature_cache', '', 'cache MFCC features to disk to speed up future training runs ont he same data. This flag specifies the path where cached features extracted from --train_files will be saved. If empty, or if online augmentation flags are enabled, caching will be disabled.')
 
     f.DEFINE_integer('feature_win_len', 32, 'feature extraction audio window length in milliseconds')
     f.DEFINE_integer('feature_win_step', 20, 'feature extraction window step length in milliseconds')