diff --git a/tooling/metamodel-generator/src/main/java/org/hibernate/processor/util/StringUtil.java b/tooling/metamodel-generator/src/main/java/org/hibernate/processor/util/StringUtil.java
index 83bc5a54fa6b..f1e9ddad5404 100644
--- a/tooling/metamodel-generator/src/main/java/org/hibernate/processor/util/StringUtil.java
+++ b/tooling/metamodel-generator/src/main/java/org/hibernate/processor/util/StringUtil.java
@@ -98,6 +98,9 @@ public static String nameToMethodName(String name) {
 	}
 
 	public static String getUpperUnderscoreCaseFromLowerCamelCase(String lowerCamelCaseString) {
+		if ( lowerCamelCaseString.length() == 1 && Character.isUpperCase( lowerCamelCaseString.charAt( 0 ) ) ) {
+			return "_" + lowerCamelCaseString;
+		}
 		final StringBuilder result = new StringBuilder();
 		int position = 0;
 		while ( position < lowerCamelCaseString.length() ) {