diff --git a/packages/types/src/Metadata/v3/Metadata.ts b/packages/types/src/Metadata/v3/Metadata.ts
index f0c1e0b2bc..5f2409703b 100644
--- a/packages/types/src/Metadata/v3/Metadata.ts
+++ b/packages/types/src/Metadata/v3/Metadata.ts
@@ -109,11 +109,15 @@ export default class MetadataV3 extends Struct implements MetadataInterface {
     return this.modules.map((mod) =>
       mod.storage.isNone
         ? []
-        : mod.storage.unwrap().map((fn) =>
-          fn.type.isMap
-            ? [fn.type.asMap.key.toString(), fn.type.asMap.value.toString()]
-            : [fn.type.asType.toString()]
-        )
+        : mod.storage.unwrap().map((fn) => {
+          if (fn.type.isMap) {
+            return [fn.type.asMap.key.toString(), fn.type.asMap.value.toString()];
+          } else if (fn.type.isDoubleMap) {
+            return [fn.type.asDoubleMap.key1.toString(), fn.type.asDoubleMap.key2.toString(), fn.type.asDoubleMap.value.toString()];
+          } else {
+            return [fn.type.asType.toString()];
+          }
+        })
     );
   }
 
diff --git a/packages/types/src/Metadata/v3/Storage.ts b/packages/types/src/Metadata/v3/Storage.ts
index c685d0e602..0a2c0d4823 100644
--- a/packages/types/src/Metadata/v3/Storage.ts
+++ b/packages/types/src/Metadata/v3/Storage.ts
@@ -11,6 +11,7 @@ import Struct from '../../codec/Struct';
 import Vector from '../../codec/Vector';
 import Bytes from '../../primitive/Bytes';
 import Text from '../../primitive/Text';
+import Type from '../../primitive/Type';
 import {
   MapType,
   PlainType,
@@ -27,25 +28,25 @@ export {
 export class DoubleMapType extends Struct {
   constructor (value?: any) {
     super({
-      key1: Text,
-      key2: Text,
-      value: Text,
+      key1: Type,
+      key2: Type,
+      value: Type,
       key2Hasher: Text
     }, value);
   }
 
   /**
-   * @description The mapped key as [[Text]]
+   * @description The mapped key as [[Type]]
    */
-  get key1 (): Text {
-    return this.get('key1') as Text;
+  get key1 (): Type {
+    return this.get('key1') as Type;
   }
 
   /**
-   * @description The mapped key as [[Text]]
+   * @description The mapped key as [[Type]]
    */
-  get key2 (): Text {
-    return this.get('key2') as Text;
+  get key2 (): Type {
+    return this.get('key2') as Type;
   }
 
   /**
@@ -56,10 +57,10 @@ export class DoubleMapType extends Struct {
   }
 
   /**
-   * @description The mapped key as [[Text]]
+   * @description The mapped key as [[Type]]
    */
-  get value (): Text {
-    return this.get('value') as Text;
+  get value (): Type {
+    return this.get('value') as Type;
   }
 }
 
@@ -125,7 +126,7 @@ export class StorageFunctionType extends EnumType<PlainType | MapType | DoubleMa
    */
   toString (): string {
     if (this.isDoubleMap) {
-      return this.asDoubleMap.toString();
+      return this.asDoubleMap.value.toString();
     }
 
     if (this.isMap) {
diff --git a/packages/types/src/Metadata/v4/Metadata.ts b/packages/types/src/Metadata/v4/Metadata.ts
index c8dc530212..5d7127f924 100644
--- a/packages/types/src/Metadata/v4/Metadata.ts
+++ b/packages/types/src/Metadata/v4/Metadata.ts
@@ -109,11 +109,15 @@ export default class MetadataV4 extends Struct implements MetadataInterface {
     return this.modules.map((mod) =>
       mod.storage.isNone
         ? []
-        : mod.storage.unwrap().map((fn) =>
-          fn.type.isMap
-            ? [fn.type.asMap.key.toString(), fn.type.asMap.value.toString()]
-            : [fn.type.asType.toString()]
-        )
+        : mod.storage.unwrap().map((fn) => {
+          if (fn.type.isMap) {
+            return [fn.type.asMap.key.toString(), fn.type.asMap.value.toString()];
+          } else if (fn.type.isDoubleMap) {
+            return [fn.type.asDoubleMap.key1.toString(), fn.type.asDoubleMap.key2.toString(), fn.type.asDoubleMap.value.toString()];
+          } else {
+            return [fn.type.asType.toString()];
+          }
+        })
     );
   }
 
diff --git a/packages/types/src/Metadata/v4/Storage.ts b/packages/types/src/Metadata/v4/Storage.ts
index e117095308..b3b1df477b 100644
--- a/packages/types/src/Metadata/v4/Storage.ts
+++ b/packages/types/src/Metadata/v4/Storage.ts
@@ -114,32 +114,32 @@ export class DoubleMapType extends Struct {
   constructor (value?: any) {
     super({
       hasher: StorageHasher,
-      key1: Text,
-      key2: Text,
-      value: Text,
+      key1: Type,
+      key2: Type,
+      value: Type,
       key2Hasher: Text
     }, value);
   }
 
   /**
-   * @description The hashing algorithm used to hash keys, as [[Text]]
+   * @description The hashing algorithm used to hash keys, as [[StorageHasher]]
    */
-  get hasher (): Text {
-    return this.get('hasher') as Text;
+  get hasher (): StorageHasher {
+    return this.get('hasher') as StorageHasher;
   }
 
   /**
-   * @description The mapped key as [[Text]]
+   * @description The mapped key as [[Type]]
    */
-  get key1 (): Text {
-    return this.get('key1') as Text;
+  get key1 (): Type {
+    return this.get('key1') as Type;
   }
 
   /**
-   * @description The mapped key as [[Text]]
+   * @description The mapped key as [[Type]]
    */
-  get key2 (): Text {
-    return this.get('key2') as Text;
+  get key2 (): Type {
+    return this.get('key2') as Type;
   }
 
   /**
@@ -150,10 +150,10 @@ export class DoubleMapType extends Struct {
   }
 
   /**
-   * @description The mapped key as [[Text]]
+   * @description The mapped key as [[Type]]
    */
-  get value (): Text {
-    return this.get('value') as Text;
+  get value (): Type {
+    return this.get('value') as Type;
   }
 }