diff --git a/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/wrapper/QuarkusJavaClientCodegen.java b/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/wrapper/QuarkusJavaClientCodegen.java
index 2f62071f..96f13924 100644
--- a/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/wrapper/QuarkusJavaClientCodegen.java
+++ b/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/wrapper/QuarkusJavaClientCodegen.java
@@ -168,7 +168,7 @@ public String toEnumVarName(String value, String datatype) {
 
         // remove _ at start and end
         enumVarName = enumVarName.replaceAll("^_+|_+$", "");
-        enumVarName = enumVarName.replaceFirst("\\d.*", "_".concat(enumVarName));
+        enumVarName = enumVarName.replaceFirst("^(\\d).*", "_".concat(enumVarName));
 
         return enumVarName.toUpperCase(Locale.ROOT);
     }
diff --git a/deployment/src/test/java/io/quarkiverse/openapi/generator/deployment/wrapper/QuarkusJavaClientCodegenTest.java b/deployment/src/test/java/io/quarkiverse/openapi/generator/deployment/wrapper/QuarkusJavaClientCodegenTest.java
index 8e56cd2d..c1a871ad 100644
--- a/deployment/src/test/java/io/quarkiverse/openapi/generator/deployment/wrapper/QuarkusJavaClientCodegenTest.java
+++ b/deployment/src/test/java/io/quarkiverse/openapi/generator/deployment/wrapper/QuarkusJavaClientCodegenTest.java
@@ -16,7 +16,10 @@ class QuarkusJavaClientCodegenTest {
             "123456,String,_123456",
             "quarkus_resources,String,QUARKUS_RESOURCES",
             "123456,Integer,NUMBER_123456", // old behavior
-            "123+123,Long,NUMBER_123PLUS_123" // old behavior
+            "123+123,Long,NUMBER_123PLUS_123", // old behavior,
+            "M123,String,M123",
+            "MA456,String,MA456",
+            "P1,String,P1",
     })
     void toEnumVarName(String value, String dataType, String expectedVarName) {