diff --git a/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/util/TestPropertyValues.java b/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/util/TestPropertyValues.java
index b9fe9bc9525..2034bda4973 100644
--- a/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/util/TestPropertyValues.java
+++ b/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/util/TestPropertyValues.java
@@ -227,7 +227,7 @@ public final class TestPropertyValues {
 
 		Type(Class<? extends MapPropertySource> sourceClass, String suffix) {
 			this.sourceClass = sourceClass;
-			this.suffix = (suffix == null ? null : "-" + suffix);
+			this.suffix = suffix;
 		}
 
 		public Class<? extends MapPropertySource> getSourceClass() {
diff --git a/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/util/TestPropertyValuesTests.java b/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/util/TestPropertyValuesTests.java
index 2845f665b48..79f6708aa42 100644
--- a/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/util/TestPropertyValuesTests.java
+++ b/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/util/TestPropertyValuesTests.java
@@ -58,7 +58,8 @@ public class TestPropertyValuesTests {
 				Type.SYSTEM_ENVIRONMENT);
 		assertThat(this.environment.getProperty("foo.bar")).isEqualTo("BAZ");
 		assertThat(this.environment.getPropertySources().contains(
-				"test-" + StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME));
+				"test-" + StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME))
+						.isTrue();
 	}
 
 	@Test