diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 5aa12521..61bbe79d 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -15,6 +15,8 @@ Changelog
 - Completion for "proxies" works now. These are classes that have a
   ``__getattr__(self, name)`` method that does a ``return getattr(x, name)``.
 - Understanding of Pytest fixtures.
+- Tensorflow, Numpy and Pandas completions should now be about 4-10x faster
+  after loading them initially.
 - Big **Script API Changes**:
     - The line and column parameters of ``jedi.Script`` are now deprecated
     - ``completions`` deprecated, use ``complete`` instead
diff --git a/test/conftest.py b/test/conftest.py
index 76ba6e1a..b023f185 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -1,16 +1,17 @@
 import os
-import re
 import subprocess
+from itertools import count
 
 import pytest
 
 from . import helpers
 from . import run
 from . import refactor
-
-import jedi
 from jedi.api.environment import InterpreterEnvironment
 from jedi.inference.compiled.value import create_from_access_path
+from jedi.inference.imports import _load_python_module
+from jedi.file_io import KnownContentFileIO
+from jedi.inference.base_value import ValueSet
 
 
 def pytest_addoption(parser):
@@ -144,3 +145,16 @@ def create_compiled_object(inference_state):
         inference_state,
         inference_state.compiled_subprocess.create_simple_object(obj)
     )
+
+
+@pytest.fixture
+def module_injector():
+    counter = count()
+
+    def module_injector(inference_state, names, code):
+        assert isinstance(names, tuple)
+        file_io = KnownContentFileIO('/foo/bar/module-injector-%s.py' % next(counter), code)
+        v = _load_python_module(inference_state, file_io, names)
+        inference_state.module_cache.add(names, ValueSet([v]))
+
+    return module_injector
diff --git a/test/test_api/test_completion.py b/test/test_api/test_completion.py
index 8aa47b0c..db078293 100644
--- a/test/test_api/test_completion.py
+++ b/test/test_api/test_completion.py
@@ -392,3 +392,33 @@ def test_fuzzy_match():
 
 def test_ellipsis_completion(Script):
     assert Script('...').complete() == []
+
+
+def test_completion_cache(Script, module_injector):
+    """
+    For some modules like numpy, tensorflow or pandas we cache docstrings and
+    type to avoid them slowing us down, because they are huge.
+    """
+    script = Script('import numpy; numpy.foo')
+    module_injector(script._inference_state, ('numpy',), 'def foo(a): "doc"')
+    c, = script.complete()
+    assert c.name == 'foo'
+    assert c.type == 'function'
+    assert c.docstring() == 'foo(a)\n\ndoc'
+
+    code = dedent('''\
+        class foo:
+            'doc2'
+            def __init__(self):
+                pass
+        ''')
+    script = Script('import numpy; numpy.foo')
+    module_injector(script._inference_state, ('numpy',), code)
+    # The outpus should still be the same
+    c, = script.complete()
+    assert c.name == 'foo'
+    assert c.type == 'function'
+    assert c.docstring() == 'foo(a)\n\ndoc'
+    cls, = c.infer()
+    assert cls.type == 'class'
+    assert cls.docstring() == 'foo()\n\ndoc2'