diff --git a/roles/stage-output/README.rst b/roles/stage-output/README.rst
index 9e5e848dd..3dd8d37bc 100644
--- a/roles/stage-output/README.rst
+++ b/roles/stage-output/README.rst
@@ -31,7 +31,7 @@ intended to be used before output fetching in a base job's post-playbook.
 .. zuul:rolevar:: extensions_to_txt
    :default: null
 
-   A list of file extensions to be replaced with .txt when staging.
+   A dict of file extensions to be replaced with .txt when staging.
    This can be useful to ensure that text files with an extension not
    registered in the web server may be viewed via browser when uploaded
    to a file server.
@@ -43,8 +43,9 @@ intended to be used before output fetching in a base job's post-playbook.
    Example:
 
      extensions_to_txt:
-     - conf
-     - log
+       conf: True
+       log: True
+       txt: False
 
      zuul.conf --(staged as)--> zuul_conf.txt
 
diff --git a/roles/stage-output/tasks/main.yaml b/roles/stage-output/tasks/main.yaml
index f56de9ae4..0dc34d2c8 100644
--- a/roles/stage-output/tasks/main.yaml
+++ b/roles/stage-output/tasks/main.yaml
@@ -5,12 +5,38 @@
   register: sources
   no_log: true
 
-- name: Build the replace regex
-  set_fact:
-    extensions_regex: "{{ extensions_to_txt | join('|') | default('__do_not_replace__') }}"
+- name: Output a warning when input is not a dict and not empty
+  debug:
+    msg: "WARNING: extensions_to_txt is a list, values defined by parents will be overwritten"
+  when:
+    - extensions_to_txt is not mapping
+    - extensions_to_txt
 
-- debug:
-    var: extensions_regex
+- name: Build the extensions list when input is not a dict (including empty)
+  set_fact:
+    extension_list: >
+      {% set extensions = ['__does_not_match__'] -%}
+      {% if extensions_to_txt -%}
+        {% set extensions = extensions_to_txt -%}
+      {% endif -%}
+      {{- extensions -}}
+  when: extensions_to_txt is not mapping
+
+- name: Build the extensions list when input is a dict
+  set_fact:
+    extension_list: >
+      {% set extensions = [] -%}
+      {% for extension, extension_bool in extensions_to_txt.items() -%}
+        {% if extension_bool -%}
+          {% set _ = extensions.append(extension) -%}
+        {% endif -%}
+      {% endfor -%}
+      {{- extensions -}}
+  when: extensions_to_txt is mapping
+
+- name: Build the extensions regular expression
+  set_fact:
+    extensions_regex: "{{ extension_list | join('|') }}"
 
 # TODO(andreaf) We might want to enforce that item.value is a valid value
 # in docs, artifacts, logs. Null case already handled.