diff --git a/src/libcalamares/partition/Tests.cpp b/src/libcalamares/partition/Tests.cpp
index bf1c433fe..a456d7e36 100644
--- a/src/libcalamares/partition/Tests.cpp
+++ b/src/libcalamares/partition/Tests.cpp
@@ -199,6 +199,16 @@ PartitionServiceTests::testFilesystemGS()
         const auto map = gs.value( "filesystem_use" ).toMap();
         QCOMPARE( map.count(), fsNames.count() + 1 );
     }
+
+    // The API says that it it case-insensitive
+    QVERIFY( !isFilesystemUsedGS( &gs, "ZFS" ) );
+    QVERIFY( isFilesystemUsedGS( &gs, "EXT4" ) );
+    QCOMPARE( isFilesystemUsedGS( &gs, "ZFS" ), isFilesystemUsedGS( &gs, "zfs" ) );
+    QCOMPARE( isFilesystemUsedGS( &gs, "EXT4" ), isFilesystemUsedGS( &gs, "ext4" ) );
+
+    useFilesystemGS( &gs, "EXT4", false );
+    QVERIFY( !isFilesystemUsedGS( &gs, "EXT4" ) );
+    QCOMPARE( isFilesystemUsedGS( &gs, "EXT4" ), isFilesystemUsedGS( &gs, "ext4" ) );
 }