diff --git a/utils/python/MITgcmutils/MITgcmutils/density.py b/utils/python/MITgcmutils/MITgcmutils/density.py
index c4d1e0c19b..939831b2fa 100644
--- a/utils/python/MITgcmutils/MITgcmutils/density.py
+++ b/utils/python/MITgcmutils/MITgcmutils/density.py
@@ -37,7 +37,7 @@
 def _check_salinity(s):
 
     sneg = s<0
-    if not np.any(sneg):
+    if np.any(sneg):
         warnings.warn('found negative salinity values')
         # warnings.warn('found negative salinity values, reset them to nan')
         # s[sneg] = np.nan