diff --git a/Makefile b/Makefile
index bfee75c1a8..0df66d5b95 100644
--- a/Makefile
+++ b/Makefile
@@ -132,7 +132,7 @@ play:
 	@echo
 
 .PHONY: check
-check: requirements flake8 checklogs
+check: check-requirements flake8 checklogs
 
 # NOTE: We pass --no-deps to the script so we don't install all the
 # package dependencies which are already installed as part of "requirements"
@@ -150,6 +150,15 @@ install-runners:
 		(. $(VIRTUALENV_DIR)/bin/activate; cd $$component; python setup.py develop --no-deps); \
 	done
 
+.PHONY: check-requirements
+check-requirements: requirements
+	@echo
+	@echo "============== CHECKING REQUIREMENTS =============="
+	@echo
+	# Update requirements and then make sure no files were changed
+	git status -- *requirements.txt */*requirements.txt | grep -q "nothing to commit"
+	@echo "All requirements files up-to-date!"
+
 .PHONY: checklogs
 checklogs:
 	@echo
@@ -849,7 +858,7 @@ debs:
 ci: ci-checks ci-unit ci-integration ci-mistral ci-packs-tests
 
 .PHONY: ci-checks
-ci-checks: compile .generated-files-check .pylint .flake8 .st2client-dependencies-check .st2common-circular-dependencies-check circle-lint-api-spec .rst-check .st2client-install-check
+ci-checks: compile .generated-files-check .pylint .flake8 check-requirements .st2client-dependencies-check .st2common-circular-dependencies-check circle-lint-api-spec .rst-check .st2client-install-check
 
 .PHONY: ci-py3-unit
 ci-py3-unit:
diff --git a/fixed-requirements.txt b/fixed-requirements.txt
index ed29375589..ad652c3456 100644
--- a/fixed-requirements.txt
+++ b/fixed-requirements.txt
@@ -42,6 +42,7 @@ tooz==1.63.1
 zake==0.2.2
 routes==2.4.1
 webob==1.8.4
+flex==6.14.0
 prance==0.9.0
 pywinrm==0.3.0
 # test requirements below
diff --git a/requirements.txt b/requirements.txt
index e4a9234547..1592c36b55 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,7 +6,7 @@ argcomplete
 bcrypt
 cryptography==2.4.2
 eventlet==0.24.1
-flex>=6.13.2,<6.15.0
+flex==6.14.0
 git+https://github.com/Kami/logshipper.git@stackstorm_patched#egg=logshipper
 git+https://github.com/StackStorm/orquesta.git@v0.4#egg=orquesta
 git+https://github.com/StackStorm/python-mistralclient.git#egg=python-mistralclient
@@ -43,7 +43,7 @@ python-json-logger
 python-statsd==2.1.0
 pytz==2018.7
 pywinrm==0.3.0
-pyyaml>=4.2b4,<5.2
+pyyaml<5.2,>=4.2b4
 rednose
 requests[security]<2.15,>=2.14.1
 retrying==1.3.3
diff --git a/scripts/travis/build.sh b/scripts/travis/build.sh
index 68647002de..81a3e8fdf9 100755
--- a/scripts/travis/build.sh
+++ b/scripts/travis/build.sh
@@ -15,7 +15,7 @@ fi
 if [ ${TASK} == 'checks' ]; then
   # compile .py files, useful as compatibility syntax check
   make compile
-  make pylint flake8 bandit .st2client-dependencies-check .st2common-circular-dependencies-check
+  make pylint flake8 bandit checkrequirements .st2client-dependencies-check .st2common-circular-dependencies-check
 elif [ ${TASK} == 'unit' ]; then
   # compile .py files, useful as compatibility syntax check
   make compile
diff --git a/st2client/requirements.txt b/st2client/requirements.txt
index e544f4f936..d4f0de457f 100644
--- a/st2client/requirements.txt
+++ b/st2client/requirements.txt
@@ -8,7 +8,7 @@ prompt-toolkit==1.0.15
 python-dateutil==2.7.5
 python-editor==1.0.3
 pytz==2018.7
-pyyaml>=4.2b4,<5.2
+pyyaml<5.2,>=4.2b4
 requests[security]<2.15,>=2.14.1
 six==1.12.0
 sseclient==0.0.19
diff --git a/st2common/requirements.txt b/st2common/requirements.txt
index 7f9445fb4f..0dbf50fa85 100644
--- a/st2common/requirements.txt
+++ b/st2common/requirements.txt
@@ -3,7 +3,7 @@ amqp==2.3.2
 apscheduler==3.5.3
 cryptography==2.4.2
 eventlet==0.24.1
-flex>=6.13.2,<6.15.0
+flex==6.14.0
 git+https://github.com/StackStorm/orquesta.git@v0.4#egg=orquesta
 greenlet==0.4.15
 ipaddr
@@ -18,7 +18,7 @@ paramiko==2.4.2
 pymongo==3.7.2
 python-dateutil==2.7.5
 python-statsd==2.1.0
-pyyaml>=4.2b4,<5.2
+pyyaml<5.2,>=4.2b4
 requests[security]<2.15,>=2.14.1
 retrying==1.3.3
 routes==2.4.1