diff --git a/.gitignore b/.gitignore
index f2c1f91..303cd33 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,6 +3,7 @@
 *.dylib
 *.so
 *.whl
+*.xlsx
 coverage.html/*
 _cache/*
 .coverage
diff --git a/_unittests/ut_validation/test_f8.py b/_unittests/ut_validation/test_f8.py
index 85f27aa..80611b5 100644
--- a/_unittests/ut_validation/test_f8.py
+++ b/_unittests/ut_validation/test_f8.py
@@ -1246,6 +1246,21 @@ def test_nan(self):
                 f8 = float32_to_fe4m3(x)
                 self.assertEqual(e, f8)
 
+    def test_negative_zero_uz(self):
+        self.assertEqual(numpy.float32(-0.0), numpy.float32(0.0))
+        self.assertEqual(float32_to_fe4m3(-0.00000001, fn=True, uz=False), 128)
+        self.assertEqual(float32_to_fe4m3(0.00000001, fn=True, uz=True), 0)
+        self.assertEqual(float32_to_fe4m3(-0.00000001, fn=True, uz=True), 0)
+        self.assertEqual(float32_to_fe5m2(-0.00000001, fn=False, uz=False), 128)
+        self.assertEqual(float32_to_fe5m2(0.00000001, fn=True, uz=True), 0)
+        self.assertEqual(float32_to_fe5m2(-0.00000001, fn=True, uz=True), 0)
+        self.assertEqual(float32_to_fe4m3(-0.0001, fn=True, uz=False), 128)
+        self.assertEqual(float32_to_fe4m3(-0.0001, fn=True, uz=True), 0)
+        self.assertEqual(search_float32_into_fe4m3(-0.0001, fn=True, uz=False), 128)
+        self.assertEqual(search_float32_into_fe4m3(-0.0001, fn=True, uz=True), 0)
+        self.assertEqual(search_float32_into_fe5m2(-0.000001, fn=False, uz=False), 128)
+        self.assertEqual(search_float32_into_fe5m2(-0.000001, fn=True, uz=True), 0)
+
 
 if __name__ == "__main__":
     unittest.main(verbosity=2)
diff --git a/onnx_array_api/validation/f8.py b/onnx_array_api/validation/f8.py
index c630807..ecd68f8 100644
--- a/onnx_array_api/validation/f8.py
+++ b/onnx_array_api/validation/f8.py
@@ -445,6 +445,11 @@ def search_float32_into_fe4m3(
             return (max_value[1] | ret) if saturate else 0x7F | ret
     f = numpy.float32(value)
     i = CastFloat8.find_closest_value(f, set_values)
+    if uz:
+        ic = i & 0x7F
+        if ic == 0:
+            return 0
+        return ic | ret
     return (i & 0x7F) | ret
 
 
@@ -488,6 +493,11 @@ def search_float32_into_fe5m2(
 
     f = numpy.float32(value)
     i = CastFloat8.find_closest_value(f, set_values)
+    if uz:
+        ic = i & 0x7F
+        if ic == 0:
+            return 0
+        return ic | ret
     return (i & 0x7F) | ret
 
 
@@ -518,47 +528,45 @@ def float32_to_fe4m3(x, fn: bool = True, uz: bool = False, saturate: bool = True
         e = (b & 0x7F800000) >> 23  # exponent
         m = b & 0x007FFFFF  # mantissa
 
-        if e != 0:
-            if e < 116:
-                pass
-            elif e < 120:
-                # denormalized number
-                ex = e - 119
-                if ex >= -2:
-                    ret |= 1 << (2 + ex)
-                    ret |= m >> (21 - ex)
-                elif m > 0:
-                    ret |= 1
-                mask = 1 << (20 - ex)
-                if m & mask and (
-                    ret & 1
-                    or m & (mask - 1) > 0
-                    or (m & mask and m & (mask << 1) and m & (mask - 1) == 0)
-                ):
+        if e < 116:
+            ret = 0
+        elif e < 120:
+            # denormalized number
+            ex = e - 119
+            if ex >= -2:
+                ret |= 1 << (2 + ex)
+                ret |= m >> (21 - ex)
+            elif m > 0:
+                ret |= 1
+            else:
+                ret = 0
+            mask = 1 << (20 - ex)
+            if m & mask and (
+                ret & 1
+                or m & (mask - 1) > 0
+                or (m & mask and m & (mask << 1) and m & (mask - 1) == 0)
+            ):
+                # rounding
+                ret += 1
+        elif e < 135:
+            # normalized number
+            ex = e - 119  # 127 - 8
+            if ex == 0:
+                ret |= 0x4
+                ret |= m >> 21
+            else:
+                ret |= ex << 3
+                ret |= m >> 20
+            if m & 0x80000 and ((m & 0x100000) or (m & 0x7FFFF)):
+                if (ret & 0x7F) < 0x7F:
                     # rounding
                     ret += 1
-            elif e < 135:
-                # normalized number
-                ex = e - 119  # 127 - 8
-                if ex == 0:
-                    ret |= 0x4
-                    ret |= m >> 21
-                else:
-                    ret |= ex << 3
-                    ret |= m >> 20
-                if m & 0x80000 and ((m & 0x100000) or (m & 0x7FFFF)):
-                    if (ret & 0x7F) < 0x7F:
-                        # rounding
-                        ret += 1
-                    elif not saturate:
-                        return 0x80
-            elif saturate:
-                ret |= 0x7F  # 01111110
-            else:
-                ret = 0x80
-        elif m == 0:
-            # -0
-            ret = 0
+                elif not saturate:
+                    return 0x80
+        elif saturate:
+            ret |= 0x7F  # 01111110
+        else:
+            ret = 0x80
         return int(ret)
     else:
         if (b & 0x7FFFFFFF) == 0x7F800000:
@@ -640,45 +648,43 @@ def float32_to_fe5m2(x, fn: bool = False, uz: bool = False, saturate: bool = Tru
         e = (b & 0x7F800000) >> 23  # exponent
         m = b & 0x007FFFFF  # mantissa
 
-        if e != 0:
-            if e < 109:
-                pass
-            elif e < 112:
-                # denormalized number
-                ex = e - 111
-                if ex >= -1:
-                    ret |= 1 << (1 + ex)
-                    ret |= m >> (22 - ex)
-                elif m > 0:
-                    ret |= 1
-                mask = 1 << (21 - ex)
-                if m & mask and (
-                    ret & 1
-                    or m & (mask - 1) > 0
-                    or (m & mask and m & (mask << 1) and m & (mask - 1) == 0)
-                ):
+        if e < 109:
+            ret = 0
+        elif e < 112:
+            # denormalized number
+            ex = e - 111
+            if ex >= -1:
+                ret |= 1 << (1 + ex)
+                ret |= m >> (22 - ex)
+            elif m > 0:
+                ret |= 1
+            else:
+                ret = 0
+            mask = 1 << (21 - ex)
+            if m & mask and (
+                ret & 1
+                or m & (mask - 1) > 0
+                or (m & mask and m & (mask << 1) and m & (mask - 1) == 0)
+            ):
+                # rounding
+                ret += 1
+        elif e < 143:
+            # normalized number
+            ex = e - 111
+            ret |= ex << 2
+            ret |= m >> 21
+            if m & 0x100000 and ((m & 0xFFFFF) or (m & 0x200000)):
+                if (ret & 0x7F) < 0x7F:
                     # rounding
                     ret += 1
-            elif e < 143:
-                # normalized number
-                ex = e - 111
-                ret |= ex << 2
-                ret |= m >> 21
-                if m & 0x100000 and ((m & 0xFFFFF) or (m & 0x200000)):
-                    if (ret & 0x7F) < 0x7F:
-                        # rounding
-                        ret += 1
-                    elif not saturate:
-                        ret = 0x80
-            elif e == 255 and m == 0:  # inf
-                ret = 0x80
-            elif saturate:
-                ret |= 0x7F  # last possible number
-            else:
-                ret = 0x80
-        elif m == 0:
-            # -0
-            ret = 0
+                elif not saturate:
+                    ret = 0x80
+        elif e == 255 and m == 0:  # inf
+            ret = 0x80
+        elif saturate:
+            ret |= 0x7F  # last possible number
+        else:
+            ret = 0x80
         return int(ret)
     elif not fn and not uz:
         if (b & 0x7FFFFFFF) == 0x7F800000: