diff --git a/scripts/rnnlm/get_unigram_probs.py b/scripts/rnnlm/get_unigram_probs.py
index e3189b26a92..52e637a0e2d 100755
--- a/scripts/rnnlm/get_unigram_probs.py
+++ b/scripts/rnnlm/get_unigram_probs.py
@@ -27,7 +27,7 @@
                     help="File that specifies multiplicities and weights for each data source: "
                     "e.g. if <text_dir> contains foo.txt and bar.txt, then should have lines "
                     "like 'foo 1 0.5' and 'bar 5 1.5'.  These "
-                    "don't have to sum to on.")
+                    "don't have to sum to one.")
 parser.add_argument("--smooth-unigram-counts", type=float, default=1.0,
                     help="Specify the constant for smoothing. We will add "
                          "(smooth_unigram_counts * num_words_with_non_zero_counts / vocab_size) "