diff --git a/deepspeech/frontend/augmentor/spec_augment.py b/deepspeech/frontend/augmentor/spec_augment.py
index a3f4e268ab2e03abf37adc05214ef1ae02970f27..7c23b628e11b5b47d59452aafc677e6aee2097ba 100644
--- a/deepspeech/frontend/augmentor/spec_augment.py
+++ b/deepspeech/frontend/augmentor/spec_augment.py
@@ -245,6 +245,8 @@ class SpecAugmentor(AugmentorBase):
         Returns:
             x (np.ndarray): `[T, F]`
         """
+        assert isinstance(x, np.ndarray)
+        assert x.ndim == 2
         x = self.time_warp(x, self.mode)
         x = self.mask_freq(x, self.replace_with_zero)
         x = self.mask_time(x, self.replace_with_zero)
diff --git a/examples/aishell/s0/conf/augmentation.json b/examples/aishell/s0/conf/augmentation.json
index 81d110b0b670636270fcdea56ada1e7e9510455d..39afe4e6a584761f9a07f68ade91cd77207aaea7 100644
--- a/examples/aishell/s0/conf/augmentation.json
+++ b/examples/aishell/s0/conf/augmentation.json
@@ -19,17 +19,18 @@
   {
     "type": "specaug",
     "params": {
-      "F": 10,
-      "T": 50,
+      "W": 5,
+      "warp_mode": "PIL",
+      "F": 30,
       "n_freq_masks": 2,
+      "T": 40,
       "n_time_masks": 2,
       "p": 1.0,
-      "W": 80,
       "adaptive_number_ratio": 0,
       "adaptive_size_ratio": 0,
       "max_n_time_masks": 20,
-      "replace_with_zero": true
+      "replace_with_zero": false
     },
     "prob": 1.0
   }
-]
+]
\ No newline at end of file
diff --git a/examples/aishell/s1/conf/augmentation.json b/examples/aishell/s1/conf/augmentation.json
index 81d110b0b670636270fcdea56ada1e7e9510455d..d0409b142906bca406ba97ff63913ada5562984e 100644
--- a/examples/aishell/s1/conf/augmentation.json
+++ b/examples/aishell/s1/conf/augmentation.json
@@ -28,7 +28,8 @@
       "adaptive_number_ratio": 0,
       "adaptive_size_ratio": 0,
       "max_n_time_masks": 20,
-      "replace_with_zero": true
+      "replace_with_zero": true,
+      "warp_mode": "PIL"
     },
     "prob": 1.0
   }
diff --git a/examples/augmentation/augmentation.json b/examples/augmentation/augmentation.json
index baf2cac3498f7dbef03b10e80614a8e059c46ac4..c99299d6cc849f132a3db80b017c444bb0b3cc85 100644
--- a/examples/augmentation/augmentation.json
+++ b/examples/augmentation/augmentation.json
@@ -52,17 +52,18 @@
   {
     "type": "specaug",
     "params": {
+      "W": 80,
+      "warp_mode": "PIL",
       "F": 10,
-      "T": 50,
       "n_freq_masks": 2,
+      "T": 50,
       "n_time_masks": 2,
       "p": 1.0,
-      "W": 80,
       "adaptive_number_ratio": 0,
       "adaptive_size_ratio": 0,
       "max_n_time_masks": 20,
-      "replace_with_zero": true
+      "replace_with_zero": false
     },
-    "prob": 0.0
+    "prob": 1.0
   }
 ]
diff --git a/examples/librispeech/s0/conf/augmentation.json b/examples/librispeech/s0/conf/augmentation.json
index 81d110b0b670636270fcdea56ada1e7e9510455d..d0409b142906bca406ba97ff63913ada5562984e 100644
--- a/examples/librispeech/s0/conf/augmentation.json
+++ b/examples/librispeech/s0/conf/augmentation.json
@@ -28,7 +28,8 @@
       "adaptive_number_ratio": 0,
       "adaptive_size_ratio": 0,
       "max_n_time_masks": 20,
-      "replace_with_zero": true
+      "replace_with_zero": true,
+      "warp_mode": "PIL"
     },
     "prob": 1.0
   }
diff --git a/examples/librispeech/s1/conf/augmentation.json b/examples/librispeech/s1/conf/augmentation.json
index 7dd158eb53406e8fad0439a2db0e654060f67523..8e6e97040190455c9bf0ed5d858e0651715413be 100644
--- a/examples/librispeech/s1/conf/augmentation.json
+++ b/examples/librispeech/s1/conf/augmentation.json
@@ -28,7 +28,8 @@
       "adaptive_number_ratio": 0,
       "adaptive_size_ratio": 0,
       "max_n_time_masks": 20,
-      "replace_with_zero": true
+      "replace_with_zero": true,
+      "warp_mode": "PIL"
     },
     "prob": 1.0
   }
diff --git a/examples/librispeech/s2/conf/augmentation.json b/examples/librispeech/s2/conf/augmentation.json
index cc8c7e00f667f5e9d850e46052f76faf1a019a53..e20fc19970ddf77c20aac43db84f340280a40364 100644
--- a/examples/librispeech/s2/conf/augmentation.json
+++ b/examples/librispeech/s2/conf/augmentation.json
@@ -11,7 +11,8 @@
       "adaptive_number_ratio": 0,
       "adaptive_size_ratio": 0,
       "max_n_time_masks": 20,
-      "replace_with_zero": true
+      "replace_with_zero": true,
+      "warp_mode": "PIL"
     },
     "prob": 1.0
   }
diff --git a/examples/timit/s1/conf/augmentation.json b/examples/timit/s1/conf/augmentation.json
index 7dd158eb53406e8fad0439a2db0e654060f67523..8e6e97040190455c9bf0ed5d858e0651715413be 100644
--- a/examples/timit/s1/conf/augmentation.json
+++ b/examples/timit/s1/conf/augmentation.json
@@ -28,7 +28,8 @@
       "adaptive_number_ratio": 0,
       "adaptive_size_ratio": 0,
       "max_n_time_masks": 20,
-      "replace_with_zero": true
+      "replace_with_zero": true,
+      "warp_mode": "PIL"
     },
     "prob": 1.0
   }
diff --git a/examples/tiny/s0/conf/augmentation.json b/examples/tiny/s0/conf/augmentation.json
index 8f9ff7fd48a2b836b5d1e41e0577984acf2ec18d..8370551667c9afbad96791bb4d357c524961313b 100644
--- a/examples/tiny/s0/conf/augmentation.json
+++ b/examples/tiny/s0/conf/augmentation.json
@@ -6,7 +6,7 @@
       "max_speed_rate": 1.1,
       "num_rates": 3
     },
-    "prob": 1.0
+    "prob": 0.0
   },
   {
     "type": "shift",
@@ -19,16 +19,18 @@
   {
     "type": "specaug",
     "params": {
-      "F": 10,
-      "T": 50,
+      "W": 5,
+      "warp_mode": "PIL",
+      "F": 30,
       "n_freq_masks": 2,
+      "T": 40,
       "n_time_masks": 2,
       "p": 1.0,
-      "W": 80,
       "adaptive_number_ratio": 0,
       "adaptive_size_ratio": 0,
       "max_n_time_masks": 20,
-      "replace_with_zero": true
+      "replace_with_zero": true,
+      "warp_mode": "PIL"
     },
     "prob": 1.0
   }
diff --git a/examples/tiny/s1/conf/augmentation.json b/examples/tiny/s1/conf/augmentation.json
index 8f9ff7fd48a2b836b5d1e41e0577984acf2ec18d..6010c2e47ec9adf3131ee834bb7d6a17741ad9c5 100644
--- a/examples/tiny/s1/conf/augmentation.json
+++ b/examples/tiny/s1/conf/augmentation.json
@@ -28,7 +28,8 @@
       "adaptive_number_ratio": 0,
       "adaptive_size_ratio": 0,
       "max_n_time_masks": 20,
-      "replace_with_zero": true
+      "replace_with_zero": true,
+      "warp_mode": "PIL"
     },
     "prob": 1.0
   }