diff --git a/README.md b/README.md
index 8ec4e4b..87e85d6 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,10 @@ Clone the repository, enter it and run
 
 `pip install .`
 
+### Requirements
+
+This project has been tested with Python 3.6 and the library versions specified in the requirements.txt, but might also work with later versions of Tensorflow.
+
 ### Models
 
 Pre-trained models in  `HDF5` format can be downloaded from here:   
diff --git a/requirements.txt b/requirements.txt
index 2f57afe..f8d696a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 numpy
-setuptools >= 41
-opencv-python-headless
-ocrd >= 2.38.0
+setuptools>=41
+ocrd==2.38.0
+opencv-python-headless==4.6.0.66
 tensorflow >= 2.4.0