diff --git a/spring-test/src/main/java/org/springframework/mock/web/MockCookie.java b/spring-test/src/main/java/org/springframework/mock/web/MockCookie.java
index 3e603040f2..0d3a1c3fcc 100644
--- a/spring-test/src/main/java/org/springframework/mock/web/MockCookie.java
+++ b/spring-test/src/main/java/org/springframework/mock/web/MockCookie.java
@@ -70,10 +70,11 @@ public class MockCookie extends Cookie {
 
 	/**
 	 * Factory method that parses the value of a "Set-Cookie" header.
-	 * @param setCookieHeader the "Set-Cookie" value
+	 * @param setCookieHeader the "Set-Cookie" value; never {@code null} or empty
 	 * @return the created cookie
 	 */
 	public static MockCookie parse(String setCookieHeader) {
+		Assert.notNull(setCookieHeader, "Set-Cookie header must not be null");
 		String[] cookieParts = setCookieHeader.split("\\s*=\\s*", 2);
 		Assert.isTrue(cookieParts.length == 2, () -> "Invalid Set-Cookie header '" + setCookieHeader + "'");
 
diff --git a/spring-test/src/test/java/org/springframework/mock/web/MockCookieTests.java b/spring-test/src/test/java/org/springframework/mock/web/MockCookieTests.java
index 2902c1b14e..d4a1410a2c 100644
--- a/spring-test/src/test/java/org/springframework/mock/web/MockCookieTests.java
+++ b/spring-test/src/test/java/org/springframework/mock/web/MockCookieTests.java
@@ -80,6 +80,13 @@ public class MockCookieTests {
 		assertEquals("Lax", cookie.getSameSite());
 	}
 
+	@Test
+	public void parseNullHeader() {
+		exception.expect(IllegalArgumentException.class);
+		exception.expectMessage("Set-Cookie header must not be null");
+		MockCookie.parse(null);
+	}
+
 	@Test
 	public void parseInvalidHeader() {
 		exception.expect(IllegalArgumentException.class);