diff --git a/doc/ext/doctest.rst b/doc/ext/doctest.rst
index c1cba088a..9ee9c1cff 100644
--- a/doc/ext/doctest.rst
+++ b/doc/ext/doctest.rst
@@ -79,9 +79,9 @@ a comma-separated list of group names.
 
          .. doctest::
             :pyversion: > 3.3
-             
+ 
      The supported operands are ``<``, ``<=``, ``==``, ``>=``, and ``>``.
-     
+
      .. versionadded:: 1.5
 
    Note that like with standard doctests, you have to use ``<BLANKLINE>`` to
diff --git a/sphinx/ext/doctest.py b/sphinx/ext/doctest.py
index 273305884..93aff532b 100644
--- a/sphinx/ext/doctest.py
+++ b/sphinx/ext/doctest.py
@@ -56,6 +56,29 @@ else:
         return text
 
 
+def compare_version(ver1, ver2, operand):
+    """Compare `ver1` to `ver2`, relying on `operand`.
+
+    Some examples:
+
+        >>> compare_version('3.3', '3.5', '<=')
+        True
+        >>> compare_version('3.3', '3.2', '<=')
+        False
+        >>> compare_version('3.3a0', '3.3', '<=')
+        True
+    """
+    if operand not in ('<=', '<', '==', '>=', '>'):
+        raise ValueError("'%s' is not a valid operand.")
+    v1 = StrictVersion(ver1)
+    v2 = StrictVersion(ver2)
+    return ((operand == '<=' and (v1 <= v2)) or
+            (operand == '<' and (v1 < v2)) or
+            (operand == '==' and (v1 == v2)) or
+            (operand == '>=' and (v1 >= v2)) or
+            (operand == '>' and (v1 > v2)))
+
+
 # set up the necessary directives
 
 class TestDirective(Directive):
@@ -114,44 +137,18 @@ class TestDirective(Directive):
         if self.name == 'doctest' and 'pyversion' in self.options:
             try:
                 option = self.options['pyversion']
-                option_strings = option.split()
-                # :pyversion: >= 3.6   -->   operand='>=', version='3.6'
-                operand, version = [item.strip() for item in option_strings]
-                if not self.proper_pyversion(operand, version):
+                # :pyversion: >= 3.6   -->   operand='>=', option_version='3.6'
+                operand, option_version = [item.strip() for item in option.split()]
+                running_version = platform.python_version()
+                if not compare_version(running_version, option_version, operand):
                     flag = doctest.OPTIONFLAGS_BY_NAME['SKIP']
                     node['options'][flag] = True  # Skip the test
             except ValueError:
                 self.state.document.reporter.warning(
-                    "'%s' is not a valid pyversion value" % option,
+                    "'%s' is not a valid pyversion option" % option,
                     line=self.lineno)
-
         return [node]
 
-    def proper_pyversion(self, operand, version):
-        """Compare `version` to the Python version, relying on `operand`.
-
-        This function is meant to be used to evaluate the doctest :pyversion:
-        option. For instance, if the doctest directive provides the option
-        :pyversion: >= 3.3, then we have to check if the running Python version
-        is greather or equal than 3.3. In that case, operand will be the string
-        '>=' and version the string '3.3'. proper_pyversion() will return True
-        if the running Python version is >= 3.3, False otherwise.
-        """
-        operands = ('<=', '<', '==', '>=', '>')
-        if operand not in operands:
-            self.document.reporter.warning(
-                "'%s' is not a valid pyversion operand.\n"
-                "Avaliable operands: %s" % (operand, operands),
-                line=self.lineno)
-            return True  # Be defensive, making the doctest to be executed
-        rv = StrictVersion(platform.python_version())  # Running version
-        sv = StrictVersion(version)  # Specified version
-        return ((operand == '<=' and (rv <= sv)) or
-                (operand == '<' and (rv < sv)) or
-                (operand == '==' and (rv == sv)) or
-                (operand == '>=' and (rv >= sv)) or
-                (operand == '>' and (rv > sv)))
-
 
 class TestsetupDirective(TestDirective):
     option_spec = {}  # type: Dict
diff --git a/tests/test_ext_doctest.py b/tests/test_ext_doctest.py
index 887fa4601..213663a2b 100644
--- a/tests/test_ext_doctest.py
+++ b/tests/test_ext_doctest.py
@@ -10,7 +10,7 @@
 """
 import platform
 import pytest
-from sphinx.ext.doctest import TestDirective as _TestDirective
+from sphinx.ext.doctest import compare_version
 
 cleanup_called = 0
 
@@ -27,19 +27,19 @@ def test_build(app, status, warning):
     assert cleanup_called == 3, 'testcleanup did not get executed enough times'
 
 
-def test_pyversion(monkeypatch):
-    monkeypatch.setattr(platform, 'python_version', lambda: '3.3')
-    td = _TestDirective(*([None] * 9))
-    assert td.proper_pyversion('<', '3.4') is True
-    assert td.proper_pyversion('<', '3.2') is False
-    assert td.proper_pyversion('<=', '3.4') is True
-    assert td.proper_pyversion('<=', '3.3') is True
-    assert td.proper_pyversion('==', '3.3') is True
-    assert td.proper_pyversion('>=', '3.4') is False
-    assert td.proper_pyversion('>=', '3.2') is True
-    assert td.proper_pyversion('>', '3.4') is False
-    assert td.proper_pyversion('>', '3.2') is True
-    assert td.proper_pyversion('>', '3.3a0') is True
+def test_compare_version():
+    assert compare_version('3.3', '3.4', '<') is True
+    assert compare_version('3.3', '3.2', '<') is False
+    assert compare_version('3.3', '3.4', '<=') is True
+    assert compare_version('3.3', '3.2', '<=') is False
+    assert compare_version('3.3', '3.3', '==') is True
+    assert compare_version('3.3', '3.4', '==') is False
+    assert compare_version('3.3', '3.2', '>=') is True
+    assert compare_version('3.3', '3.4', '>=') is False
+    assert compare_version('3.3', '3.2', '>') is True
+    assert compare_version('3.3', '3.4', '>') is False
+    with pytest.raises(ValueError):
+        compare_version('3.3', '3.4', '+')
 
 
 def cleanup_call():