diff --git a/requirements.txt b/requirements.txt
index 2a520f8..6b278a0 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,7 @@ simpy
 networkx>=2.0
 numpy
 matplotlib
-pyyaml
+pyyaml>=5.1
 pandas>=0.23
 scipy==1.2.1 # scipy 1.3.0rc1 is not compatible with salib
 SALib>=1.3
diff --git a/soil/serialization.py b/soil/serialization.py
index 884e2f0..fca71c5 100644
--- a/soil/serialization.py
+++ b/soil/serialization.py
@@ -55,7 +55,7 @@ def load_file(infile):
 
 
 def load_string(string):
-    yield from yaml.load_all(string)
+    yield from yaml.load_all(string, Loader=yaml.FullLoader)
 
 
 def expand_template(config):