diff --git a/guessit/rules/common/formatters.py b/guessit/rules/common/formatters.py
index 434c20b..2a64dee 100644
--- a/guessit/rules/common/formatters.py
+++ b/guessit/rules/common/formatters.py
@@ -25,7 +25,7 @@ def _potential_before(i, input_string):
     :return:
     :rtype: bool
     """
-    return i - 2 >= 0 and input_string[i] in seps and input_string[i - 2] in seps and input_string[i - 1] not in seps
+    return i - 1 >= 0 and input_string[i] in seps and input_string[i - 2] in seps and input_string[i - 1] not in seps
 
 
 def _potential_after(i, input_string):
diff --git a/guessit/test/episodes.yml b/guessit/test/episodes.yml
index 0d0bb51..b280b83 100644
--- a/guessit/test/episodes.yml
+++ b/guessit/test/episodes.yml
@@ -4592,7 +4592,7 @@
   type: episode
 
 ? S.W.A.T.2017.S01E21.Treibjagd.German.Dubbed.DL.AmazonHD.x264-TVS
-: title: S W.A.T.
+: title: S.W.A.T.
   year: 2017
   season: 1
   episode: 21
@@ -4605,3 +4605,15 @@
   video_codec: H.264
   release_group: TVS
   type: episode
+
+? S.W.A.T.2017.S01E16.READNFO.720p.HDTV.x264-KILLERS
+: title: S.W.A.T.
+  year: 2017
+  season: 1
+  episode: 16
+  other: Read NFO
+  screen_size: 720p
+  source: HDTV
+  video_codec: H.264
+  release_group: KILLERS
+  type: episode