diff --git a/buildSrc/src/main/java/org/springframework/boot/build/bom/bomr/UpgradeApplicator.java b/buildSrc/src/main/java/org/springframework/boot/build/bom/bomr/UpgradeApplicator.java
index 8e1df88e379..2f47151f183 100644
--- a/buildSrc/src/main/java/org/springframework/boot/build/bom/bomr/UpgradeApplicator.java
+++ b/buildSrc/src/main/java/org/springframework/boot/build/bom/bomr/UpgradeApplicator.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -65,14 +65,19 @@ class UpgradeApplicator {
 		String gradlePropertiesContents = new String(Files.readAllBytes(this.gradleProperties), StandardCharsets.UTF_8);
 		String modified = gradlePropertiesContents.replace(property + "=" + upgrade.getLibrary().getVersion(),
 				property + "=" + upgrade.getVersion());
-		Files.write(this.gradleProperties, modified.getBytes(StandardCharsets.UTF_8), StandardOpenOption.CREATE);
+		overwrite(this.gradleProperties, modified);
 	}
 
 	private void updateBuildFile(Upgrade upgrade, String buildFileContents) throws IOException {
 		String modified = buildFileContents.replace(
 				"library(\"" + upgrade.getLibrary().getName() + "\", \"" + upgrade.getLibrary().getVersion() + "\")",
 				"library(\"" + upgrade.getLibrary().getName() + "\", \"" + upgrade.getVersion() + "\")");
-		Files.write(this.buildFile, modified.getBytes(StandardCharsets.UTF_8), StandardOpenOption.CREATE);
+		overwrite(this.buildFile, modified);
+	}
+
+	private void overwrite(Path target, String content) throws IOException {
+		Files.write(target, content.getBytes(StandardCharsets.UTF_8), StandardOpenOption.WRITE,
+				StandardOpenOption.TRUNCATE_EXISTING);
 	}
 
 }
diff --git a/buildSrc/src/test/java/org/springframework/boot/build/bom/bomr/UpgradeApplicatorTests.java b/buildSrc/src/test/java/org/springframework/boot/build/bom/bomr/UpgradeApplicatorTests.java
index 4a39c841097..aef6b32ff52 100644
--- a/buildSrc/src/test/java/org/springframework/boot/build/bom/bomr/UpgradeApplicatorTests.java
+++ b/buildSrc/src/test/java/org/springframework/boot/build/bom/bomr/UpgradeApplicatorTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2020 the original author or authors.
+ * Copyright 2012-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -32,6 +32,7 @@ import org.springframework.boot.build.bom.bomr.version.DependencyVersion;
 import org.springframework.util.FileCopyUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.entry;
 
 /**
  * Tests for {@link UpgradeApplicator}.
@@ -47,13 +48,14 @@ class UpgradeApplicatorTests {
 	void whenUpgradeIsAppliedToLibraryWithVersionThenBomIsUpdated() throws IOException {
 		File bom = new File(this.temp, "bom.gradle");
 		FileCopyUtils.copy(new File("src/test/resources/bom.gradle"), bom);
+		String originalContents = new String(Files.readAllBytes(bom.toPath()), StandardCharsets.UTF_8);
 		File gradleProperties = new File(this.temp, "gradle.properties");
 		FileCopyUtils.copy(new File("src/test/resources/gradle.properties"), gradleProperties);
 		new UpgradeApplicator(bom.toPath(), gradleProperties.toPath())
 				.apply(new Upgrade(new Library("ActiveMQ", DependencyVersion.parse("5.15.11"), null, null),
 						DependencyVersion.parse("5.16")));
 		String bomContents = new String(Files.readAllBytes(bom.toPath()), StandardCharsets.UTF_8);
-		assertThat(bomContents).contains("library(\"ActiveMQ\", \"5.16\")");
+		assertThat(bomContents.length()).isEqualTo(originalContents.length() - 3);
 	}
 
 	@Test
@@ -62,14 +64,14 @@ class UpgradeApplicatorTests {
 		FileCopyUtils.copy(new File("src/test/resources/bom.gradle"), bom);
 		File gradleProperties = new File(this.temp, "gradle.properties");
 		FileCopyUtils.copy(new File("src/test/resources/gradle.properties"), gradleProperties);
-		new UpgradeApplicator(bom.toPath(), gradleProperties.toPath())
-				.apply(new Upgrade(new Library("Kotlin", DependencyVersion.parse("1.3.70"), null, null),
-						DependencyVersion.parse("1.3.71")));
+		new UpgradeApplicator(bom.toPath(), gradleProperties.toPath()).apply(new Upgrade(
+				new Library("Kotlin", DependencyVersion.parse("1.3.70"), null, null), DependencyVersion.parse("1.4")));
 		Properties properties = new Properties();
 		try (InputStream in = new FileInputStream(gradleProperties)) {
 			properties.load(in);
 		}
-		assertThat(properties).containsEntry("kotlinVersion", "1.3.71");
+		assertThat(properties).containsOnly(entry("a", "alpha"), entry("b", "bravo"), entry("kotlinVersion", "1.4"),
+				entry("t", "tango"));
 	}
 
 }