diff --git a/modules/jenkins/manifests/job_builder.pp b/modules/jenkins/manifests/job_builder.pp
index bdae7d2962..8721db9520 100644
--- a/modules/jenkins/manifests/job_builder.pp
+++ b/modules/jenkins/manifests/job_builder.pp
@@ -4,8 +4,12 @@ class jenkins::job_builder (
     $password,
 ) {
 
-  package { 'python-yaml':
-    ensure => "present",
+  # A lot of things need yaml, be conservative requiring this package to avoid
+  # conflicts with other modules.
+  if ! defined(Package['python-yaml']) {
+    package { 'python-yaml':
+      ensure => "present",
+    }
   }
 
   package { "python-jenkins":
diff --git a/modules/zuul/manifests/init.pp b/modules/zuul/manifests/init.pp
index be35a0fc3b..3e4f859954 100644
--- a/modules/zuul/manifests/init.pp
+++ b/modules/zuul/manifests/init.pp
@@ -12,12 +12,20 @@ class zuul (
                "python-lockfile",
                "python-paramiko",
                "python-paste",
-               "python-yaml"]
+              ]
 
   package { $packages:
     ensure => "present",
   }
 
+  # A lot of things need yaml, be conservative requiring this package to avoid
+  # conflicts with other modules.
+  if ! defined(Package['python-yaml']) {
+    package { 'python-yaml':
+      ensure => "present",
+    }
+  }
+
   # Packages that need to be installed from pip
   $pip_packages = ["GitPython"]