diff --git a/tests/test_conditional_steps.py b/tests/test_conditional_steps.py
index 2d402a91..95d03361 100644
--- a/tests/test_conditional_steps.py
+++ b/tests/test_conditional_steps.py
@@ -223,17 +223,66 @@ def test_prebuild_clean(test_env: ConditionalStepsTestEnv,
         test_env.check_fail(steps_info)
 
 
+def test_conditional_step_critical(test_env: ConditionalStepsTestEnv) -> None:
+    steps_info: StepsInfo = test_env.build_conditional_steps_info(is_conditional_step_passed=False)
+    steps_info.conditional_step.critical = True
+    test_env.check_success(steps_info)
+    assert test_env.captured_out.out
+    assert "WARNING" in test_env.captured_out.out
+
+
 # TODO: implement support of conditional step with children
 #  https://github.com/Samsung/Universum/issues/709
-def test_conditional_step_with_children(test_env: ConditionalStepsTestEnv) -> None:
+def test_conditional_step_with_children(test_env: ConditionalStepsTestEnv, capsys: pytest.CaptureFixture) -> None:
     steps_info: StepsInfo = test_env.build_conditional_steps_info(is_conditional_step_passed=True)
     steps_info.conditional_step.children = Configuration([Step(name=" dummy child 1"), Step(name=" dummy child 2")])
     test_env.check_fail(steps_info)
 
+    captured_out = capsys.readouterr()
+    assert "not supported" in captured_out.out
 
-def test_conditional_step_critical(test_env: ConditionalStepsTestEnv) -> None:
-    steps_info: StepsInfo = test_env.build_conditional_steps_info(is_conditional_step_passed=False)
-    steps_info.conditional_step.critical = True
-    test_env.check_success(steps_info)
-    assert test_env.captured_out.out
-    assert "WARNING" in test_env.captured_out.out
+
+# TODO: implement support of conditional steps addition and multiplication
+#  https://github.com/Samsung/Universum/issues/709
+def test_add_step_to_conditional(test_env: ConditionalStepsTestEnv, capsys: pytest.CaptureFixture) -> None:
+    config_lines: List[str] = [
+        "from universum.configuration_support import Configuration, Step",
+        "true_branch_config = Configuration([Step(name='true branch')])",
+        "conditional_step = Step(name='conditional', if_succeeded=true_branch_config)",
+        "another_step = Step(name='another step')",
+        "configs = Configuration([conditional_step + another_step])"
+    ]
+    config: str = "\n".join(config_lines)
+    test_env.configs_file.write_text(config, "utf-8")
+    test_env.run(expect_failure=True)
+
+    captured_out = capsys.readouterr()
+    assert "not supported" in captured_out.out
+
+
+# TODO: during implementation of the full conditional steps addition support, refactor this test to avoid direct usage
+#       of the ConditionalStepsTestEnv "internal" API (underscored methods) and config building duplication
+#  https://github.com/Samsung/Universum/issues/709
+def test_add_conditional_to_step(test_env: ConditionalStepsTestEnv, capsys: pytest.CaptureFixture) -> None:
+    # pylint: disable = protected-access
+    steps_info = test_env.build_conditional_steps_info(is_conditional_step_passed=True)
+    true_branch_config = test_env._build_configuration_string(steps_info.true_branch_steps)
+    config_lines: List[str] = [
+        "from universum.configuration_support import Configuration, Step",
+        f"true_branch_config = {true_branch_config}",
+        f"conditional_step = Step(**{str(steps_info.conditional_step)})",
+        "another_step = Step(name='another step')",
+
+        # `true/false_branch_steps` should be Python objects from this script
+        "conditional_step.is_conditional = True",
+        "conditional_step.if_succeeded = true_branch_config",
+
+        "configs = Configuration([another_step + conditional_step])"
+    ]
+    config: str = "\n".join(config_lines)
+    test_env.configs_file.write_text(config, "utf-8")
+    test_env.run()
+
+    test_env._check_conditional_step_artifacts_present(steps_info)
+    test_env._check_executed_step_artifacts_present(steps_info)
+    # pylint: enable = protected-access
diff --git a/universum/configuration_support.py b/universum/configuration_support.py
index 43831a8c..3b731a7e 100644
--- a/universum/configuration_support.py
+++ b/universum/configuration_support.py
@@ -3,6 +3,7 @@
 from warnings import warn
 import copy
 import os
+from .lib.ci_exception import CriticalCiException
 
 
 __all__ = [
@@ -397,6 +398,9 @@ def __add__(self, other: 'Step') -> 'Step':
         >>> step2 + step1
         {'name': 'barfoo', 'command': ['bar', 'foo'], 'critical': True, 'background': True, 'my_var1': 'barfoo', 'my_var2': 'baz'}
         """
+        if self.is_conditional:
+            # TODO: https://github.com/Samsung/Universum/issues/709
+            raise CriticalCiException("Conditional steps addition is not supported yet")
         return Step(
             name=self.name + other.name,
             command=self.command + other.command,
diff --git a/universum/modules/launcher.py b/universum/modules/launcher.py
index c195c14f..e72a35b4 100644
--- a/universum/modules/launcher.py
+++ b/universum/modules/launcher.py
@@ -415,7 +415,7 @@ def process_project_configs(self) -> configuration_support.Configuration:
             raise CriticalCiException(text)
 
         if self._is_conditional_step_with_children_present(self.project_config):
-            raise CriticalCiException("Conditional step doesn't support children configuration")
+            raise CriticalCiException("Conditional steps with child configurations are not supported")
         self._warn_if_critical_conditional_steps_present(self.project_config)
 
         return self.project_config