diff --git a/packages/env/CHANGELOG.md b/packages/env/CHANGELOG.md
index d7e9a6ee70cb6f..13b1b7b801fee0 100644
--- a/packages/env/CHANGELOG.md
+++ b/packages/env/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Bug Fixes
+
+-   "mappings" sources are now downloaded if they contain non-local sources.
+
 ## 3.0.0 (2020-12-17)
 
 ### Breaking Changes
diff --git a/packages/env/lib/download-sources.js b/packages/env/lib/download-sources.js
index d74f33d826484d..e4396b01146d52 100644
--- a/packages/env/lib/download-sources.js
+++ b/packages/env/lib/download-sources.js
@@ -55,6 +55,7 @@ module.exports = function downloadSources( config, spinner ) {
 	for ( const env of Object.values( config.env ) ) {
 		env.pluginSources.forEach( addSource );
 		env.themeSources.forEach( addSource );
+		Object.values( env.mappings ).forEach( addSource );
 		addSource( env.coreSource );
 	}