diff --git a/ethosu/vela/test/test_tflite_model_semantic.py b/ethosu/vela/test/test_tflite_model_semantic.py
index 2d6ca15..e290dd2 100644
--- a/ethosu/vela/test/test_tflite_model_semantic.py
+++ b/ethosu/vela/test/test_tflite_model_semantic.py
@@ -413,12 +413,17 @@
 
 
 def test_constraint_alpha_valid():
-    # Alpha cannot be negative
-    op = testutil.create_elemwise_op(Op.LeakyRelu, "op", [2, 2], None, [2, 2])
+    # Alpha can only be negative for int8 and uint8
+    op = testutil.create_elemwise_op(Op.LeakyRelu, "op", [2, 2], None, [2, 2], DataType.int16)
     op.attrs["alpha"] = 0
     assert semantic_checker.is_operator_semantic_valid(op)
     op.attrs["alpha"] = -1
     assert not semantic_checker.is_operator_semantic_valid(op)
+    op = testutil.create_elemwise_op(Op.LeakyRelu, "op", [2, 2], None, [2, 2], DataType.int8)
+    op.attrs["alpha"] = 0
+    assert semantic_checker.is_operator_semantic_valid(op)
+    op.attrs["alpha"] = -1
+    assert semantic_checker.is_operator_semantic_valid(op)
 
 
 def test_constraint_hardswish_dtype():
diff --git a/ethosu/vela/tflite_model_semantic.py b/ethosu/vela/tflite_model_semantic.py
index c811a0d..e0541df 100644
--- a/ethosu/vela/tflite_model_semantic.py
+++ b/ethosu/vela/tflite_model_semantic.py
@@ -532,10 +532,11 @@
 
     @staticmethod
     def constraint_alpha_valid(op):
-        "Alpha must not be negative"
+        "Alpha only allowed to be negative if IFM is int8 or uint8"
         alpha = op.attrs["alpha"]
-        valid = alpha >= 0
-        return valid, f"Op has alpha={alpha}"
+        ifm_dtype = op.ifm.dtype
+        valid = ifm_dtype == DataType.int8 or ifm_dtype == DataType.uint8 or alpha >= 0
+        return valid, f"Op has alpha={alpha} and ifm_dtype={ifm_dtype} "
 
     @staticmethod
     def constraint_keep_dim_ifm_ofm(op):