diff --git a/__tests__/base.js b/__tests__/base.js
index 105bdc32..e37dba2a 100644
--- a/__tests__/base.js
+++ b/__tests__/base.js
@@ -1282,6 +1282,23 @@ function runBaseTest(name, useProxies, autoFreeze, useListener) {
 			expect(nextState).not.toEqual(baseState)
 		})
 
+		it("should handle equality correctly - 3", () => {
+			const baseState = {
+				x: "s1",
+				y: 1,
+				z: NaN
+			}
+			const nextState = produce(baseState, draft => {
+				draft.x = "s2"
+				draft.y = 1
+				draft.z = NaN
+				expect(draft[DRAFT_STATE].assigned_.x).toBe(true)
+				expect(draft[DRAFT_STATE].assigned_.y).toBe(undefined)
+				expect(draft[DRAFT_STATE].assigned_.z).toBe(undefined)
+			})
+			expect(nextState.x).toBe("s2")
+		})
+
 		// AKA: recursive produce calls
 		describe("nested producers", () => {
 			describe("when base state is not a draft", () => {
diff --git a/src/core/proxy.ts b/src/core/proxy.ts
index 7e6503a9..1d9f61da 100644
--- a/src/core/proxy.ts
+++ b/src/core/proxy.ts
@@ -158,11 +158,11 @@ export const objectTraps: ProxyHandler<ProxyState> = {
 		}
 
 		if (
-			state.copy_![prop] === value &&
+			(state.copy_![prop] === value &&
+				// special case: handle new props with value 'undefined'
+				(value !== undefined || prop in state.copy_)) ||
 			// special case: NaN
-			typeof value !== "number" &&
-			// special case: handle new props with value 'undefined'
-			(value !== undefined || prop in state.copy_)
+			(Number.isNaN(value) && Number.isNaN(state.copy_![prop]))
 		)
 			return true