diff --git a/requirements.txt b/requirements.txt
index 2aded32369..5f0de0f90c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -28,7 +28,7 @@ iso8601
 psutil
 fb-re2>=1.0.6
 paho-mqtt
-cherrypy
+cherrypy==18.3.0; # last version to support cheroot below
 ws4py
 routes
 pathspec
diff --git a/tools/pip.sh b/tools/pip.sh
index 47b5027f7f..469d119eb5 100755
--- a/tools/pip.sh
+++ b/tools/pip.sh
@@ -39,6 +39,9 @@ then
 fi
 pip install $*
 
+# Fail-fast if pip detects conflicts
+pip check
+
 # Check if we're installing zuul. If so install the managed ansible as well.
 if echo "$*" | grep -vq requirements.txt; then
     zuul-manage-ansible -v