diff --git a/skyvern/forge/sdk/workflow/models/block.py b/skyvern/forge/sdk/workflow/models/block.py
index 95e0c9e8a..39a0d7a47 100644
--- a/skyvern/forge/sdk/workflow/models/block.py
+++ b/skyvern/forge/sdk/workflow/models/block.py
@@ -29,7 +29,7 @@ import pyotp
 import structlog
 from charset_normalizer import from_bytes
 from email_validator import EmailNotValidError, validate_email
-from jinja2 import StrictUndefined, TemplateSyntaxError
+from jinja2 import StrictUndefined, TemplateSyntaxError, UndefinedError
 from jinja2.sandbox import SandboxedEnvironment
 from opentelemetry import trace as otel_trace
 from playwright.async_api import Page
@@ -803,12 +803,14 @@ class BaseTaskBlock(Block):
                     formatted_error_code = self.format_block_parameter_template_from_workflow_run_context(
                         error_code, workflow_run_context
                     )
-                except TemplateSyntaxError as exc:
+                except (TemplateSyntaxError, UndefinedError) as exc:
+                    error_detail = exc.message if isinstance(exc, UndefinedError) else exc.message
+                    error_location = "" if isinstance(exc, UndefinedError) else f" (line {exc.lineno})"
                     raise FailedToFormatJinjaStyleParameter(
                         template=error_code,
                         msg=(
-                            "Invalid Jinja syntax in error_code_mapping key "
-                            f"'{error_code}': {exc.message} (line {exc.lineno})"
+                            "Invalid Jinja template in error_code_mapping key "
+                            f"'{error_code}': {error_detail}{error_location}"
                         ),
                     ) from exc
 
@@ -816,12 +818,14 @@ class BaseTaskBlock(Block):
                     formatted_error_description = self.format_block_parameter_template_from_workflow_run_context(
                         error_description, workflow_run_context
                     )
-                except TemplateSyntaxError as exc:
+                except (TemplateSyntaxError, UndefinedError) as exc:
+                    error_detail = exc.message if isinstance(exc, UndefinedError) else exc.message
+                    error_location = "" if isinstance(exc, UndefinedError) else f" (line {exc.lineno})"
                     raise FailedToFormatJinjaStyleParameter(
                         template=error_description,
                         msg=(
-                            "Invalid Jinja syntax in error_code_mapping value for key "
-                            f"'{error_code}': {exc.message} (line {exc.lineno})"
+                            "Invalid Jinja template in error_code_mapping value for key "
+                            f"'{error_code}': {error_detail}{error_location}"
                         ),
                     ) from exc
 
diff --git a/tests/unit/test_task_block_error_code_mapping_template_errors.py b/tests/unit/test_task_block_error_code_mapping_template_errors.py
index 6758acec5..51111a04d 100644
--- a/tests/unit/test_task_block_error_code_mapping_template_errors.py
+++ b/tests/unit/test_task_block_error_code_mapping_template_errors.py
@@ -2,8 +2,11 @@ from datetime import datetime, timezone
 from unittest.mock import MagicMock
 
 import pytest
+from jinja2 import StrictUndefined
+from jinja2.sandbox import SandboxedEnvironment
 
 from skyvern.forge.sdk.workflow.exceptions import FailedToFormatJinjaStyleParameter
+from skyvern.forge.sdk.workflow.models import block as block_module
 from skyvern.forge.sdk.workflow.models.block import TaskBlock
 from skyvern.forge.sdk.workflow.models.parameter import OutputParameter, ParameterType
 
@@ -79,3 +82,29 @@ def test_error_code_mapping_key_reports_precise_jinja_syntax_error() -> None:
     error_message = str(exc_info.value)
     assert "error_code_mapping key '{{ error code }}'" in error_message
     assert "expected token 'end of print statement'" in error_message
+
+
+def test_error_code_mapping_value_reports_undefined_variable_in_strict_mode(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    strict_env = SandboxedEnvironment(undefined=StrictUndefined)
+    strict_env.filters["json"] = block_module._json_type_filter
+    monkeypatch.setattr(block_module, "jinja_sandbox_env", strict_env)
+
+    block = TaskBlock(
+        label="block_1",
+        block_type="task",
+        title="Test block",
+        output_parameter=_build_output_parameter(),
+        error_code_mapping={
+            "ACCOUNT_GROUP_NOT_FOUND": "return this error when {{ nonexistent_output }} is missing"
+        },
+    )
+    ctx = _build_mock_context()
+
+    with pytest.raises(FailedToFormatJinjaStyleParameter) as exc_info:
+        block.format_potential_template_parameters(ctx)
+
+    error_message = str(exc_info.value)
+    assert "error_code_mapping value for key 'ACCOUNT_GROUP_NOT_FOUND'" in error_message
+    assert "'nonexistent_output' is undefined" in error_message