diff --git a/src/containers/blocks.jsx b/src/containers/blocks.jsx
index 98a01db1bf1cf1819da808b4d3c2e9b08129bdef..c982bfeccfed36055895a0a1dd3e117066734176 100644
--- a/src/containers/blocks.jsx
+++ b/src/containers/blocks.jsx
@@ -87,6 +87,7 @@ class Blocks extends React.Component {
     componentDidMount () {
         this.ScratchBlocks.FieldColourSlider.activateEyedropper_ = this.props.onActivateColorPicker;
         this.ScratchBlocks.Procedures.externalProcedureDefCallback = this.props.onActivateCustomProcedures;
+        this.ScratchBlocks.ScratchMsgs.setLocale(this.props.locale);
 
         const workspaceConfig = defaultsDeep({},
             Blocks.defaultOptions,
@@ -526,7 +527,7 @@ Blocks.propTypes = {
     extensionLibraryVisible: PropTypes.bool,
     isRtl: PropTypes.bool,
     isVisible: PropTypes.bool,
-    locale: PropTypes.string,
+    locale: PropTypes.string.isRequired,
     messages: PropTypes.objectOf(PropTypes.string),
     onActivateColorPicker: PropTypes.func,
     onActivateCustomProcedures: PropTypes.func,