diff --git a/src/num_sys_class.py b/src/num_sys_class.py
index 7c10838..14efc2e 100644
--- a/src/num_sys_class.py
+++ b/src/num_sys_class.py
@@ -350,6 +350,10 @@ def quant_bfloat_py(self, float_arr, n_bits, n_exp):
         power_exp_diff = torch.exp2(exp_diff)
         mant_adj = mant / power_exp_diff
 
+        # handle mantissa underflow after shifting
+        # values that become subnormal should be clamped to maintain valid representation
+        mant_adj[mant_adj < 1.0] = 0.0
+
         exp_adj = torch.full(exp.shape, shared_exp, device=float_arr.device)
 
         # exp should not be larger than max_exp
@@ -415,6 +419,10 @@ def quant_bfloat_meta_py(self, float_arr, n_bits=8, n_exp=3):
         power_exp_diff = torch.exp2(exp_diff)
         mant_adj = mant / power_exp_diff
 
+        # handle mantissa underflow after shifting
+        # values that become subnormal should be clamped to maintain valid representation
+        mant_adj[mant_adj < 1.0] = 0.0
+
         exp_adj = torch.full(exp.shape, shared_exp, device=float_arr.device)
 
         # exp should not be larger than max_exp