diff --git a/requirements.txt b/requirements.txt
index ace996ad954..a3c8d27ebee 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,5 +4,6 @@ matplotlib==1.5.3
 pyqtgraph==0.10.0
 PyVISA==1.8
 PyQt5==5.7
+sip==4.18.1
 QtPy==1.1.2
 h5py==2.6.0