diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/SystemEnvironmentPropertyMapper.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/SystemEnvironmentPropertyMapper.java
index 74a13a4803e..3f4ae6323b3 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/SystemEnvironmentPropertyMapper.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/SystemEnvironmentPropertyMapper.java
@@ -75,7 +75,9 @@ final class SystemEnvironmentPropertyMapper implements PropertyMapper {
 	private String convertName(ConfigurationPropertyName name, int numberOfElements) {
 		StringBuilder result = new StringBuilder();
 		for (int i = 0; i < numberOfElements; i++) {
-			result.append(result.length() == 0 ? "" : "_");
+			if (result.length() > 0) {
+				result.append("_");
+			}
 			result.append(name.getElement(i, Form.UNIFORM).toUpperCase());
 		}
 		return result.toString();
@@ -84,7 +86,9 @@ final class SystemEnvironmentPropertyMapper implements PropertyMapper {
 	private String convertLegacyName(ConfigurationPropertyName name) {
 		StringBuilder result = new StringBuilder();
 		for (int i = 0; i < name.getNumberOfElements(); i++) {
-			result.append(result.length() == 0 ? "" : "_");
+			if (result.length() > 0) {
+				result.append("_");
+			}
 			result.append(convertLegacyNameElement(name.getElement(i, Form.ORIGINAL)));
 		}
 		return result.toString();