diff --git a/lib/xmet/rawins.py b/lib/xmet/rawins.py
index 4defa4f..cd4c551 100644
--- a/lib/xmet/rawins.py
+++ b/lib/xmet/rawins.py
@@ -195,7 +195,7 @@ class RawinsObs():
         sounding.samples.append(sample)
 
         for i in range(5, len(self.values), 3):
-            if len(self.values) <= i+2 or self.values[i][-1] == '=':
+            if len(self.values) < i+3 or self.values[i][-1] == '=':
                 break
 
             sample = self.parse_sample_values(self.values[i:i+3])