diff --git a/test/data/manifests/fedora-boot.json b/test/data/manifests/fedora-boot.json
index 2598024a..7ef563ef 100644
--- a/test/data/manifests/fedora-boot.json
+++ b/test/data/manifests/fedora-boot.json
@@ -660,7 +660,7 @@
       {
         "name": "org.osbuild.locale",
         "options": {
-          "language": "en_US"
+          "language": "en_US.UTF-8"
         }
       },
       {
diff --git a/test/data/manifests/fedora-boot.mpp.json b/test/data/manifests/fedora-boot.mpp.json
index fe8b5f23..788b812e 100644
--- a/test/data/manifests/fedora-boot.mpp.json
+++ b/test/data/manifests/fedora-boot.mpp.json
@@ -47,7 +47,7 @@
       {
         "name": "org.osbuild.locale",
         "options": {
-          "language": "en_US"
+          "language": "en_US.UTF-8"
         }
       },
       {
diff --git a/test/data/manifests/fedora-container.json b/test/data/manifests/fedora-container.json
index 2bc0e357..d3060224 100644
--- a/test/data/manifests/fedora-container.json
+++ b/test/data/manifests/fedora-container.json
@@ -527,7 +527,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         }
       ]
diff --git a/test/data/manifests/fedora-container.mpp.json b/test/data/manifests/fedora-container.mpp.json
index d9123875..aa60bf94 100644
--- a/test/data/manifests/fedora-container.mpp.json
+++ b/test/data/manifests/fedora-container.mpp.json
@@ -70,7 +70,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         }
       ]
diff --git a/test/data/manifests/fedora-ostree-bootiso.json b/test/data/manifests/fedora-ostree-bootiso.json
index 48a36e7f..3c19d44b 100644
--- a/test/data/manifests/fedora-ostree-bootiso.json
+++ b/test/data/manifests/fedora-ostree-bootiso.json
@@ -776,7 +776,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         },
         {
@@ -1695,7 +1695,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         },
         {
diff --git a/test/data/manifests/fedora-ostree-bootiso.mpp.json b/test/data/manifests/fedora-ostree-bootiso.mpp.json
index 358caa30..c9a4baa5 100644
--- a/test/data/manifests/fedora-ostree-bootiso.mpp.json
+++ b/test/data/manifests/fedora-ostree-bootiso.mpp.json
@@ -89,7 +89,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         },
         {
@@ -383,7 +383,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         },
         {
diff --git a/test/data/manifests/fedora-ostree-commit.json b/test/data/manifests/fedora-ostree-commit.json
index 2014386b..12f01ed4 100644
--- a/test/data/manifests/fedora-ostree-commit.json
+++ b/test/data/manifests/fedora-ostree-commit.json
@@ -661,7 +661,7 @@
       {
         "name": "org.osbuild.locale",
         "options": {
-          "language": "en_US"
+          "language": "en_US.UTF-8"
         }
       },
       {
diff --git a/test/data/manifests/fedora-ostree-commit.mpp.json b/test/data/manifests/fedora-ostree-commit.mpp.json
index b25553c7..7edd94d3 100644
--- a/test/data/manifests/fedora-ostree-commit.mpp.json
+++ b/test/data/manifests/fedora-ostree-commit.mpp.json
@@ -46,7 +46,7 @@
       {
         "name": "org.osbuild.locale",
         "options": {
-          "language": "en_US"
+          "language": "en_US.UTF-8"
         }
       },
       {
diff --git a/test/data/manifests/fedora-ostree-container.json b/test/data/manifests/fedora-ostree-container.json
index ddc551d2..39d2535b 100644
--- a/test/data/manifests/fedora-ostree-container.json
+++ b/test/data/manifests/fedora-ostree-container.json
@@ -726,7 +726,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         },
         {
@@ -978,7 +978,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         }
       ]
diff --git a/test/data/manifests/fedora-ostree-container.mpp.json b/test/data/manifests/fedora-ostree-container.mpp.json
index 33f3c45a..54fe57cc 100644
--- a/test/data/manifests/fedora-ostree-container.mpp.json
+++ b/test/data/manifests/fedora-ostree-container.mpp.json
@@ -57,7 +57,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         },
         {
@@ -167,7 +167,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         }
       ]
diff --git a/test/data/manifests/fedora-ostree-image.json b/test/data/manifests/fedora-ostree-image.json
index d6e3c447..c1ecb768 100644
--- a/test/data/manifests/fedora-ostree-image.json
+++ b/test/data/manifests/fedora-ostree-image.json
@@ -720,7 +720,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         },
         {
diff --git a/test/data/manifests/fedora-ostree-image.mpp.json b/test/data/manifests/fedora-ostree-image.mpp.json
index c13d1ab0..7ca742ef 100644
--- a/test/data/manifests/fedora-ostree-image.mpp.json
+++ b/test/data/manifests/fedora-ostree-image.mpp.json
@@ -177,7 +177,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         },
         {
diff --git a/test/data/manifests/fedora-ostree-tarball.json b/test/data/manifests/fedora-ostree-tarball.json
index 5619c92b..bec79ba9 100644
--- a/test/data/manifests/fedora-ostree-tarball.json
+++ b/test/data/manifests/fedora-ostree-tarball.json
@@ -726,7 +726,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         },
         {
diff --git a/test/data/manifests/fedora-ostree-tarball.mpp.json b/test/data/manifests/fedora-ostree-tarball.mpp.json
index f7dd6219..7ce5ee46 100644
--- a/test/data/manifests/fedora-ostree-tarball.mpp.json
+++ b/test/data/manifests/fedora-ostree-tarball.mpp.json
@@ -57,7 +57,7 @@
         {
           "type": "org.osbuild.locale",
           "options": {
-            "language": "en_US"
+            "language": "en_US.UTF-8"
           }
         },
         {