diff --git a/types/slate/index.d.ts b/types/slate/index.d.ts
index 7b93e66314..31233b8541 100644
--- a/types/slate/index.d.ts
+++ b/types/slate/index.d.ts
@@ -13,6 +13,7 @@
 //                 Han Jeon <https://github.com/hanstar17>
 //                 Kay Delaney <https://github.com/kaydelaney>
 //                 Yuichiro Tsuchiya <https://github.com/tuttieee>
+//                 Kamil Kamiński <https://github.com/0ctothorp>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.8
 import * as Immutable from "immutable";
@@ -491,7 +492,7 @@ declare class BaseNode extends Immutable.Record({}) {
     createSelection(properties: SelectionProperties | SelectionJSON | Selection | Range): Selection;
     descendants(options?: IterableOptions): Iterable<[Node, Immutable.List<number>]>;
     filterDescendants(predicate?: (node: Node, path: Immutable.List<number>) => boolean): Immutable.List<Node>;
-    findDescendants(predicate?: (node: Node, path: Immutable.List<number>) => boolean): Node | null;
+    findDescendant(predicate?: (node: Node, path: Immutable.List<number>) => boolean): Node | null;
     forEachDescendant(predicate?: (node: Node, path: Immutable.List<number>) => boolean): void;
     getActiveMarksAtRange(range: RangeTypeProperties | RangeTypeJSON | RangeType): Immutable.Set<Mark>;
     getAncestors(path: Path): Immutable.List<Node> | null;
diff --git a/types/slate/slate-tests.ts b/types/slate/slate-tests.ts
index 9f1b483c81..09f15faf67 100644
--- a/types/slate/slate-tests.ts
+++ b/types/slate/slate-tests.ts
@@ -31,12 +31,12 @@ data['foo'];
 
 const value = Value.create({ data });
 
-const node: BlockJSON = {
-	object: "block",
-	type: "paragraph",
-	nodes: [
-		{
-			object: "text",
+const nodeJSON: BlockJSON = {
+    object: "block",
+    type: "paragraph",
+    nodes: [
+        {
+            object: "text",
             key: "a",
             text: "example",
             marks: [{
@@ -44,16 +44,26 @@ const node: BlockJSON = {
                 type: "mark",
                 object: "mark"
             }]
-		}
-	]
+        }
+    ]
 };
 
 const doc = Document.fromJSON({
-	object: "document",
-	data: {},
-	nodes: [node]
+    object: "document",
+    data: {},
+    nodes: [nodeJSON]
 });
 
+const node = new Block(nodeJSON);
+
+doc.findDescendant();
+doc.findDescendant(node => node.object === 'block' && node.type === 'paragraph');
+doc.findDescendant((node, path) => true);
+
+node.findDescendant();
+node.findDescendant(node => node.object === 'block');
+node.findDescendant((node, path) => false);
+
 const schema: SchemaProperties = {
     document: {
         nodes: [
@@ -168,13 +178,13 @@ editor
 .flush()
 .focus()
 .insertBlock({
-	type: "image",
-	key: "b",
-	data: {
-		src: "http://placekitten.com/200/300",
-		alt: "Kittens",
-		className: "img-responsive"
-	}
+    type: "image",
+    key: "b",
+    data: {
+        src: "http://placekitten.com/200/300",
+        alt: "Kittens",
+        className: "img-responsive"
+    }
 })
 .insertBlockAtRange(range, "text")
 .insertFragment(doc)