diff --git a/backend/src/main/java/edu/internet2/tier/shibboleth/admin/ui/configuration/InternationalizationConfiguration.java b/backend/src/main/java/edu/internet2/tier/shibboleth/admin/ui/configuration/InternationalizationConfiguration.java
index dc8599865..0064433fa 100644
--- a/backend/src/main/java/edu/internet2/tier/shibboleth/admin/ui/configuration/InternationalizationConfiguration.java
+++ b/backend/src/main/java/edu/internet2/tier/shibboleth/admin/ui/configuration/InternationalizationConfiguration.java
@@ -20,6 +20,7 @@ public MappedResourceBundleMessageSource messageSource() {
         MappedResourceBundleMessageSource source = new MappedResourceBundleMessageSource();
         source.setBasenames("i18n/messages");
         source.setUseCodeAsDefaultMessage(true);
+        source.setFallbackToSystemLocale(false);
         return source;
     }
 }
diff --git a/backend/src/test/groovy/edu/internet2/tier/shibboleth/admin/ui/controller/InternationalizationMessagesControllerTests.groovy b/backend/src/test/groovy/edu/internet2/tier/shibboleth/admin/ui/controller/InternationalizationMessagesControllerTests.groovy
index 16626c2e8..722b929c8 100644
--- a/backend/src/test/groovy/edu/internet2/tier/shibboleth/admin/ui/controller/InternationalizationMessagesControllerTests.groovy
+++ b/backend/src/test/groovy/edu/internet2/tier/shibboleth/admin/ui/controller/InternationalizationMessagesControllerTests.groovy
@@ -110,7 +110,7 @@ class InternationalizationMessagesControllerTests extends Specification {
         when:
         def result = mockMvc.perform(
                 get(messagesUrl)
-                        .header("Accept-Language", "es"))
+                        .header("Accept-Language", "ja_JP"))
 
         then:
         result.andExpect(content().json(expectedEnglishResult))