diff --git a/packages/slate/src/transforms/general.ts b/packages/slate/src/transforms/general.ts
index 9e77a759b..a3d17a4ec 100755
--- a/packages/slate/src/transforms/general.ts
+++ b/packages/slate/src/transforms/general.ts
@@ -212,18 +212,32 @@ export const GeneralTransforms: GeneralTransforms = {
 
         if (newProperties == null) {
           selection = newProperties
-        } else if (selection == null) {
-          if (!Range.isRange(newProperties)) {
-            throw new Error(
-              `Cannot apply an incomplete "set_selection" operation properties ${JSON.stringify(
-                newProperties
-              )} when there is no current selection.`
-            )
+        } else {
+          if (selection == null) {
+            if (!Range.isRange(newProperties)) {
+              throw new Error(
+                `Cannot apply an incomplete "set_selection" operation properties ${JSON.stringify(
+                  newProperties
+                )} when there is no current selection.`
+              )
+            }
+
+            selection = { ...newProperties }
           }
 
-          selection = newProperties
-        } else {
-          Object.assign(selection, newProperties)
+          for (const key in newProperties) {
+            const value = newProperties[key]
+
+            if (value == null) {
+              if (key === 'anchor' || key === 'focus') {
+                throw new Error(`Cannot remove the "${key}" selection property`)
+              }
+
+              delete selection[key]
+            } else {
+              selection[key] = value
+            }
+          }
         }
 
         break
diff --git a/packages/slate/test/operations/set_selection/custom-props.tsx b/packages/slate/test/operations/set_selection/custom-props.tsx
new file mode 100644
index 000000000..eba804c35
--- /dev/null
+++ b/packages/slate/test/operations/set_selection/custom-props.tsx
@@ -0,0 +1,29 @@
+/** @jsx jsx */
+import { jsx } from 'slate-hyperscript'
+import { Transforms, Editor } from 'slate'
+
+export const input = (
+  <editor>
+    <element>
+      a<cursor />
+    </element>
+  </editor>
+)
+
+export const operations = [
+  {
+    type: 'set_selection',
+    oldProperties: {},
+    newProperties: { custom: 123 },
+  },
+]
+
+export const output = (
+  <editor>
+    <element>
+      a<cursor />
+    </element>
+  </editor>
+)
+
+Transforms.setSelection(output, { custom: 123 })
diff --git a/packages/slate/test/operations/set_selection/remove.tsx b/packages/slate/test/operations/set_selection/remove.tsx
new file mode 100644
index 000000000..f0b65d06c
--- /dev/null
+++ b/packages/slate/test/operations/set_selection/remove.tsx
@@ -0,0 +1,29 @@
+/** @jsx jsx */
+import { jsx } from 'slate-hyperscript'
+import { Transforms, Editor } from 'slate'
+
+export const input = (
+  <editor>
+    <element>
+      a<cursor />
+    </element>
+  </editor>
+)
+
+Transforms.setSelection(input, { custom: 123 })
+
+export const operations = [
+  {
+    type: 'set_selection',
+    oldProperties: {},
+    newProperties: { custom: null },
+  },
+]
+
+export const output = (
+  <editor>
+    <element>
+      a<cursor />
+    </element>
+  </editor>
+)