diff --git a/README.rst b/README.rst
index c75f4db..885cd17 100644
--- a/README.rst
+++ b/README.rst
@@ -18,6 +18,8 @@ so that changes are only merged if they pass tests.
 Requirements
 ------------
 
+* pip3 to be installed if using zuul_install_method: (git|pip)
+
 See `bindep.txt` for role dependencies.
 
 Packages
diff --git a/tasks/install.yaml b/tasks/install.yaml
index d540fdf..576cf7e 100644
--- a/tasks/install.yaml
+++ b/tasks/install.yaml
@@ -25,4 +25,12 @@
   with_items: "{{ zuul_build_depends }}"
   when: zuul_install_method == 'git'
 
+- name: Define zuul_pip_executable if needed.
+  set_fact:
+    zuul_pip_executable: pip3
+  when:
+    - zuul_install_method == 'git' or zuul_install_method == 'pip'
+    - zuul_pip_virtualenv_python is not defined
+    - zuul_pip_executable is not defined
+
 - include: "install/{{ zuul_install_method }}.yaml"