diff --git a/conda_smithy/lint_recipe.py b/conda_smithy/lint_recipe.py
index 4876a53da..8a1cc01b4 100644
--- a/conda_smithy/lint_recipe.py
+++ b/conda_smithy/lint_recipe.py
@@ -149,6 +149,14 @@ def lintify(meta, recipe_dir=None):
     except RuntimeError as e:
         lints.append(str(e))
 
+    # 13: If cython/numpy is a build-dependency then python should be a run-time
+    # dependency. This ensures that packages will be marked correctly by conda
+    build_deps = ['cython', 'numpy x.x']
+    need_python_run_time = any([dep in requirements_section.get('build', '') for dep in build_deps])
+    if need_python_run_time and 'python' not in requirements_section.get('run', ''):
+        lints.append("Found python related compilation requirement "
+                     "please add python as a run-time dependency")
+
     return lints
 
 
diff --git a/conda_smithy/tests/test_lint_recipe.py b/conda_smithy/tests/test_lint_recipe.py
index 24f14c345..96dea7bcd 100644
--- a/conda_smithy/tests/test_lint_recipe.py
+++ b/conda_smithy/tests/test_lint_recipe.py
@@ -253,6 +253,15 @@ def test_end_empty_line(self):
                 else:
                     self.assertIn(expected_message, lints)
 
+    def test_implicit_python_run_time_dependency(self):
+        build_deps = ['cython', 'numpy x.x']
+        expected_message = ("Found python related compilation requirement "
+                            "please add python as a run-time dependency")
+        for dep in build_deps:
+            meta = {'requirements': {'build': [dep, 'python']}}
+            lints = linter.lintify(meta)
+            self.assertIn(expected_message, lints)
+
 
 class TestCLI_recipe_lint(unittest.TestCase):
     def test_cli_fail(self):