diff --git a/src/defense/evasion_defense.py b/src/defense/evasion_defense.py
index 52a9a0f..7604edc 100644
--- a/src/defense/evasion_defense.py
+++ b/src/defense/evasion_defense.py
@@ -94,6 +94,7 @@ def __init__(
             num_levels: int = 32
     ):
         super().__init__()
+        assert num_levels > 1
         self.num_levels = num_levels
 
     def pre_batch(
@@ -112,9 +113,12 @@ def quantize(
     ):
         x_min = x.min()
         x_max = x.max()
-        x_normalized = (x - x_min) / (x_max - x_min)
-        x_quantized = torch.round(x_normalized * (self.num_levels - 1)) / (self.num_levels - 1)
-        x_quantized = x_quantized * (x_max - x_min) + x_min
+        if x_min != x_max:
+            x_normalized = (x - x_min) / (x_max - x_min)
+            x_quantized = torch.round(x_normalized * (self.num_levels - 1)) / (self.num_levels - 1)
+            x_quantized = x_quantized * (x_max - x_min) + x_min
+        else:
+            x_quantized = x
         return x_quantized