diff --git a/miplearn/components/steps/convert_tight.py b/miplearn/components/steps/convert_tight.py
index 7adc84d..9466ffd 100644
--- a/miplearn/components/steps/convert_tight.py
+++ b/miplearn/components/steps/convert_tight.py
@@ -113,7 +113,7 @@ class ConvertTightIneqsIntoEqsStep(Component):
                     continue
                 if category not in y:
                     y[category] = []
-                if slack <= self.slack_tolerance:
+                if 0 <= slack <= self.slack_tolerance:
                     y[category] += [[1]]
                 else:
                     y[category] += [[0]]