diff --git a/maskrcnn_benchmark/config/defaults.py b/maskrcnn_benchmark/config/defaults.py
index 4b142a675..367337f0d 100644
--- a/maskrcnn_benchmark/config/defaults.py
+++ b/maskrcnn_benchmark/config/defaults.py
@@ -60,6 +60,8 @@
 _C.INPUT.SATURATION = 0.0
 _C.INPUT.HUE = 0.0
 
+# Flips
+_C.INPUT.HORIZONTAL_FLIP_PROB_TRAIN = 0.5
 _C.INPUT.VERTICAL_FLIP_PROB_TRAIN = 0.0
 
 # -----------------------------------------------------------------------------
diff --git a/maskrcnn_benchmark/data/transforms/build.py b/maskrcnn_benchmark/data/transforms/build.py
index 52385ea7d..098da11d4 100644
--- a/maskrcnn_benchmark/data/transforms/build.py
+++ b/maskrcnn_benchmark/data/transforms/build.py
@@ -6,7 +6,7 @@ def build_transforms(cfg, is_train=True):
     if is_train:
         min_size = cfg.INPUT.MIN_SIZE_TRAIN
         max_size = cfg.INPUT.MAX_SIZE_TRAIN
-        flip_horizontal_prob = 0.5  # cfg.INPUT.FLIP_PROB_TRAIN
+        flip_horizontal_prob = cfg.INPUT.HORIZONTAL_FLIP_PROB_TRAIN
         flip_vertical_prob = cfg.INPUT.VERTICAL_FLIP_PROB_TRAIN
         brightness = cfg.INPUT.BRIGHTNESS
         contrast = cfg.INPUT.CONTRAST