diff --git a/README.md b/README.md
index c45df2b..baeb0e7 100644
--- a/README.md
+++ b/README.md
@@ -84,37 +84,44 @@ By default a single string is returned. Can be set to `false` to instead return
 #### spacerNoNeighbour
 
 Type: `string`<br>
-Default: `   `
+Default: `   `
 
 Prefix for depth level when no further neighbour is present.
 
 #### spacerNeighbour
 
 Type: `string`<br>
-Default: `│  `
+Default: `│  `
 
 Prefix for depth level when a further neighbour is present.
 
 #### keyNoNeighbour
 
 Type: `string`<br>
-Default: `└─ `
+Default: `└─ `
 
 Prefix for key when no further neighbour is present.
 
 #### keyNeighbour
 
 Type: `string`<br>
-Default: `├─ `
+Default: `├─ `
 
 Prefix for key when a further neighbour is present.
 
+#### separator
+
+Type: `string`<br>
+Default: `: `
+
+Used to separate node key from node value.
+
 #### renderFn
 
 Type: `function`<br>
-Default: ``(node) => (['boolean', 'string', 'number'].includes(typeof node) ? `: ${node}` : '')``
+Default: `(node) => (['boolean', 'string', 'number'].includes(typeof node) ? node : undefined)`
 
-Can be used to overwrite the node rendering logic.
+Can be used to overwrite the node rendering logic. Node is rendered if result is not equal `undefined`.
 
 #### sortFn
 
diff --git a/src/index.js b/src/index.js
index 97a8f8f..bd7da6b 100644
--- a/src/index.js
+++ b/src/index.js
@@ -7,17 +7,19 @@ const buildCtx = (opts) => {
     spacerNeighbour: '│  ',
     keyNoNeighbour: '└─ ',
     keyNeighbour: '├─ ',
-    renderFn: (node) => (['boolean', 'string', 'number'].includes(typeof node) ? `: ${node}` : ''),
+    separator: ': ',
+    renderFn: (node) => (['boolean', 'string', 'number'].includes(typeof node) ? node : undefined),
     sortFn: null,
     breakCircularWith: ' (circular ref.)',
     ...opts
   };
-  assert(Object.keys(ctx).length === 8, 'Unexpected Option(s) provided');
+  assert(Object.keys(ctx).length === 9, 'Unexpected Option(s) provided');
   assert(typeof ctx.joined === 'boolean', 'Option "joined" has invalid format');
   assert(typeof ctx.spacerNoNeighbour === 'string', 'Option "spacerNoNeighbour" has invalid format');
   assert(typeof ctx.spacerNeighbour === 'string', 'Option "spacerNeighbour" has invalid format');
   assert(typeof ctx.keyNoNeighbour === 'string', 'Option "keyNoNeighbour" has invalid format');
   assert(typeof ctx.keyNeighbour === 'string', 'Option "keyNeighbour" has invalid format');
+  assert(typeof ctx.separator === 'string', 'Option "separator" has invalid format');
   assert(typeof ctx.renderFn === 'function', 'Option "renderFn" has invalid format');
   assert(typeof ctx.sortFn === 'function' || ctx.sortFn === null, 'Option "sortFn" has invalid format');
   assert(
@@ -31,6 +33,11 @@ export default (tree, opts = {}) => {
   const ctx = buildCtx(opts);
   const result = [];
 
+  const rootRendered = ctx.renderFn(tree);
+  if (rootRendered !== undefined) {
+    result.push(String(rootRendered));
+  }
+
   const sort = (input) => (ctx.sortFn === null ? input.reverse() : input.sort((a, b) => ctx.sortFn(b, a)));
 
   const neighbours = [];
@@ -42,11 +49,12 @@ export default (tree, opts = {}) => {
     const isCircular = ctx.breakCircularWith !== null && lookup.includes(node);
 
     neighbours[key.length - 1] = keys.length !== 0 && keys[keys.length - 1].length === key.length;
+    const nodeRendered = ctx.renderFn(node);
     result.push([
       neighbours.slice(0, key.length - 1).map((n) => (n ? ctx.spacerNeighbour : ctx.spacerNoNeighbour)).join(''),
       neighbours[key.length - 1] ? ctx.keyNeighbour : ctx.keyNoNeighbour,
       key[key.length - 1],
-      ctx.renderFn(node),
+      nodeRendered === undefined ? '' : `${ctx.separator}${node}`,
       isCircular ? ctx.breakCircularWith : ''
     ].join(''));
 
diff --git a/test/index.spec.js b/test/index.spec.js
index e16439d..c67d434 100644
--- a/test/index.spec.js
+++ b/test/index.spec.js
@@ -139,8 +139,9 @@ describe('Testing Treeify', () => {
         9: null
       }
     }, {
-      renderFn: (node) => `: ${node}`
+      renderFn: (node) => node
     })).to.deep.equal([
+      '[object Object]',
       '├─ 1: [object Object]',
       '│  ├─ 2: [object Object]',
       '│  │  └─ 3: null',