diff --git a/paper-api/src/main/java/org/bukkit/configuration/file/YamlConfiguration.java b/paper-api/src/main/java/org/bukkit/configuration/file/YamlConfiguration.java
index df250bf41..f9abe6991 100644
--- a/paper-api/src/main/java/org/bukkit/configuration/file/YamlConfiguration.java
+++ b/paper-api/src/main/java/org/bukkit/configuration/file/YamlConfiguration.java
@@ -144,8 +144,8 @@ public class YamlConfiguration extends FileConfiguration {
     private void fromNodeTree(@NotNull MappingNode input, @NotNull ConfigurationSection section) {
         constructor.flattenMapping(input);
         for (NodeTuple nodeTuple : input.getValue()) {
-            ScalarNode key = (ScalarNode) nodeTuple.getKeyNode();
-            String keyString = key.getValue();
+            Node key = nodeTuple.getKeyNode();
+            String keyString = String.valueOf(constructor.construct(key));
             Node value = nodeTuple.getValueNode();
 
             while (value instanceof AnchorNode) {
@@ -169,7 +169,9 @@ public class YamlConfiguration extends FileConfiguration {
 
     private boolean hasSerializedTypeKey(MappingNode node) {
         for (NodeTuple nodeTuple : node.getValue()) {
-            String key = ((ScalarNode) nodeTuple.getKeyNode()).getValue();
+            Node keyNode = nodeTuple.getKeyNode();
+            if (!(keyNode instanceof ScalarNode)) continue;
+            String key = ((ScalarNode) keyNode).getValue();
             if (key.equals(ConfigurationSerialization.SERIALIZED_TYPE_KEY)) {
                 return true;
             }
@@ -180,7 +182,7 @@ public class YamlConfiguration extends FileConfiguration {
     private MappingNode toNodeTree(@NotNull ConfigurationSection section) {
         List<NodeTuple> nodeTuples = new ArrayList<>();
         for (Map.Entry<String, Object> entry : section.getValues(false).entrySet()) {
-            ScalarNode key = (ScalarNode) representer.represent(entry.getKey());
+            Node key = representer.represent(entry.getKey());
             Node value;
             if (entry.getValue() instanceof ConfigurationSection) {
                 value = toNodeTree((ConfigurationSection) entry.getValue());
diff --git a/paper-api/src/main/java/org/bukkit/configuration/file/YamlConstructor.java b/paper-api/src/main/java/org/bukkit/configuration/file/YamlConstructor.java
index 7052f8a56..092599425 100644
--- a/paper-api/src/main/java/org/bukkit/configuration/file/YamlConstructor.java
+++ b/paper-api/src/main/java/org/bukkit/configuration/file/YamlConstructor.java
@@ -22,7 +22,7 @@ public class YamlConstructor extends SafeConstructor {
         super.flattenMapping(node);
     }
 
-    @NotNull
+    @Nullable
     public Object construct(@NotNull Node node) {
         return constructObject(node);
     }
diff --git a/paper-api/src/test/java/org/bukkit/configuration/file/YamlConfigurationTest.java b/paper-api/src/test/java/org/bukkit/configuration/file/YamlConfigurationTest.java
index a0ff42abd..3522baa0a 100644
--- a/paper-api/src/test/java/org/bukkit/configuration/file/YamlConfigurationTest.java
+++ b/paper-api/src/test/java/org/bukkit/configuration/file/YamlConfigurationTest.java
@@ -174,4 +174,31 @@ public class YamlConfigurationTest extends FileConfigurationTest {
 
         assertEquals(expected, result);
     }
+
+    @Test
+    public void testUnusualMappingKeys() throws InvalidConfigurationException {
+        YamlConfiguration config = getConfig();
+        String content = "[1]: odd\n"
+                + "{2}: choice\n"
+                + "\"3\": of\n"
+                + "4: keys\n"
+                + "null: A\n"
+                + "'null': B\n"
+                + "!!null null: C\n"
+                + "'!!null': X\n";
+        // The keys are parsed as arbitrary Yaml types and then converted to their String representation during config loading.
+        // Consequently, the String representation used by the loaded config might be different to how these keys were originally represented.
+        // Since SnakeYaml does not preserve the original representation in its parsed node tree, we are also not able to reconstruct the original keys during config loading.
+        config.loadFromString(content);
+
+        // This difference in representations also becomes apparent when the config is written back.
+        // Also note: All keys that are parsed as null overwrite each other's values.
+        String expected = "'[1]': odd\n"
+                + "'{2=null}': choice\n"
+                + "'3': of\n"
+                + "'4': keys\n"
+                + "'null': C\n"
+                + "'!!null': X\n";
+        assertEquals(expected, config.saveToString());
+    }
 }