diff --git a/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java b/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java
index 914ce0d5743..e51a8b0ad24 100644
--- a/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java
+++ b/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java
@@ -331,6 +331,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	public void reset() {
 		resetBuffer();
 		this.characterEncoding = null;
+		this.charset = false;
 		this.contentLength = 0;
 		this.contentType = null;
 		this.locale = Locale.getDefault();
diff --git a/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java b/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java
index 2045ecb28a5..37887d88c0f 100644
--- a/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java
+++ b/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java
@@ -481,4 +481,27 @@ class MockHttpServletResponseTests {
 		assertThat(((MockCookie) cookie).getSameSite()).isEqualTo("Lax");
 	}
 
+	@Test  // gh-25501
+	void resetResetsCharset() {
+		assertThat(response.isCharset()).isFalse();
+		response.setCharacterEncoding("UTF-8");
+		assertThat(response.isCharset()).isTrue();
+		assertThat(response.getCharacterEncoding()).isEqualTo("UTF-8");
+		response.setContentType("text/plain");
+		assertThat(response.getContentType()).isEqualTo("text/plain");
+		String contentTypeHeader = response.getHeader(CONTENT_TYPE);
+		assertThat(contentTypeHeader).isEqualTo("text/plain;charset=UTF-8");
+
+		response.reset();
+
+		assertThat(response.isCharset()).isFalse();
+		// Do not invoke setCharacterEncoding() since that sets the charset flag to true.
+		// response.setCharacterEncoding("UTF-8");
+		response.setContentType("text/plain");
+		assertThat(response.isCharset()).isFalse(); // should still be false
+		assertThat(response.getContentType()).isEqualTo("text/plain");
+		contentTypeHeader = response.getHeader(CONTENT_TYPE);
+		assertThat(contentTypeHeader).isEqualTo("text/plain");
+	}
+
 }
diff --git a/spring-web/src/testFixtures/java/org/springframework/web/testfixture/servlet/MockHttpServletResponse.java b/spring-web/src/testFixtures/java/org/springframework/web/testfixture/servlet/MockHttpServletResponse.java
index d9fe018ebe7..94358fd786f 100644
--- a/spring-web/src/testFixtures/java/org/springframework/web/testfixture/servlet/MockHttpServletResponse.java
+++ b/spring-web/src/testFixtures/java/org/springframework/web/testfixture/servlet/MockHttpServletResponse.java
@@ -331,6 +331,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	public void reset() {
 		resetBuffer();
 		this.characterEncoding = null;
+		this.charset = false;
 		this.contentLength = 0;
 		this.contentType = null;
 		this.locale = Locale.getDefault();