diff --git a/tests/requirements.txt b/tests/requirements.txt
index 2af4e6074..dacaea9d5 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,9 +1,9 @@
 keras>=2.1,<2.2
-pycodestyle<2.4.0,>=2.0.0
+pycodestyle>=2.4,<2.5
 pydocstyle>=2.1,<2.2
-pytest>=3.4,<3.5
+pytest>=3.5,<3.6
 pytest-cache>=1.0,<1.1
 pytest-cov>=2.5,<2.6
 pytest-xdist>=1.22,<1.23
 sphinx>=1.7,<1.8
-yapf>=0.20,<0.21
\ No newline at end of file
+yapf>=0.21,<0.22