diff --git a/tests/spec_decode/e2e/test_multistep_correctness.py b/tests/spec_decode/e2e/test_multistep_correctness.py
index 6d385184d264a..ccc8e745ab371 100644
--- a/tests/spec_decode/e2e/test_multistep_correctness.py
+++ b/tests/spec_decode/e2e/test_multistep_correctness.py
@@ -57,6 +57,9 @@ from .conftest import (get_output_from_llm_generator,
 
         # Skip cuda graph recording for fast test.
         "enforce_eager": True,
+
+        # The original model is float32, keep it for numerical stability.
+        "dtype": "float32",
     }])
 @pytest.mark.parametrize(
     "per_test_common_llm_kwargs",
@@ -139,6 +142,9 @@ def test_spec_decode_e2e_with_detokenization(test_llm_generator,
 
         # Print spec metrics.
         "disable_log_stats": False,
+
+        # The original model is float32, keep it for numerical stability.
+        "dtype": "float32",
     }])
 @pytest.mark.parametrize(
     "per_test_common_llm_kwargs",
@@ -216,6 +222,9 @@ def test_spec_decode_e2e_greedy_correctness_tiny_model_bs1(
 
         # Print spec metrics.
         "disable_log_stats": False,
+
+        # The original model is float32, keep it for numerical stability.
+        "dtype": "float32",
     }])
 @pytest.mark.parametrize(
     "per_test_common_llm_kwargs",
@@ -279,6 +288,9 @@ def test_spec_decode_e2e_greedy_correctness_tiny_model_large_bs(
     [{
         # Skip cuda graph recording for fast test.
         "enforce_eager": True,
+
+        # The original model is float32, keep it for numerical stability.
+        "dtype": "float32",
     }])
 @pytest.mark.parametrize(
     "per_test_common_llm_kwargs",
@@ -464,6 +476,8 @@ def test_spec_decode_e2e_greedy_correctness_real_model_large_bs(
 
         # Skip cuda graph recording for fast test.
         "enforce_eager": True,
+        # The original model is float32, keep it for numerical stability.
+        "dtype": "float32",
     }])
 @pytest.mark.parametrize("per_test_common_llm_kwargs", [
     {
@@ -523,6 +537,8 @@ def test_spec_decode_e2e_greedy_correctness_with_preemption(
 
         # Skip cuda graph recording for fast test.
         "enforce_eager": True,
+        # The original model is float32, keep it for numerical stability.
+        "dtype": "float32",
     }])
 @pytest.mark.parametrize(
     "per_test_common_llm_kwargs",
@@ -589,6 +605,8 @@ def test_spec_decode_different_block_size(vllm_runner, common_llm_kwargs,
 
         # Skip cuda graph recording for fast test.
         "enforce_eager": True,
+        # The original model is float32, keep it for numerical stability.
+        "dtype": "float32",
     }])
 @pytest.mark.parametrize("per_test_common_llm_kwargs", [{}])
 @pytest.mark.parametrize("baseline_llm_kwargs", [{}])
@@ -655,6 +673,8 @@ def test_skip_speculation(vllm_runner, common_llm_kwargs,
 
         # Skip cuda graph recording for fast test.
         "enforce_eager": True,
+        # The original model is float32, keep it for numerical stability.
+        "dtype": "float32",
     }])
 @pytest.mark.parametrize("per_test_common_llm_kwargs", [{}])
 @pytest.mark.parametrize("baseline_llm_kwargs", [{}])
@@ -706,6 +726,8 @@ def test_disable_speculation(vllm_runner, common_llm_kwargs,
 
         # Skip cuda graph recording for fast test.
         "enforce_eager": True,
+        # The original model is float32, keep it for numerical stability.
+        "dtype": "float32",
     }])
 @pytest.mark.parametrize("per_test_common_llm_kwargs", [{}])
 @pytest.mark.parametrize("baseline_llm_kwargs", [{}])
@@ -763,6 +785,8 @@ def test_many_k(vllm_runner, common_llm_kwargs, per_test_common_llm_kwargs,
 
         # Skip cuda graph recording for fast test.
         "enforce_eager": True,
+        # The original model is float32, keep it for numerical stability.
+        "dtype": "float32",
     }])
 @pytest.mark.parametrize("per_test_common_llm_kwargs", [{}])
 @pytest.mark.parametrize("baseline_llm_kwargs", [{}])