diff --git a/core/deployment/src/main/java/io/quarkus/deployment/configuration/RunTimeConfigurationGenerator.java b/core/deployment/src/main/java/io/quarkus/deployment/configuration/RunTimeConfigurationGenerator.java
index b841edc24ee9f..111b6171fdba6 100644
--- a/core/deployment/src/main/java/io/quarkus/deployment/configuration/RunTimeConfigurationGenerator.java
+++ b/core/deployment/src/main/java/io/quarkus/deployment/configuration/RunTimeConfigurationGenerator.java
@@ -403,11 +403,6 @@ public static final class GenerateOperation implements AutoCloseable {
                 clinit.invokeStaticMethod(CU_ADD_SOURCE_FACTORY_PROVIDER, buildTimeBuilder,
                         clinit.newInstance(RCSF_NEW, clinit.load(discoveredConfigSourceFactory)));
             }
-            // add mappings
-            for (ConfigClassWithPrefix configMapping : staticConfigMappings) {
-                clinit.invokeStaticMethod(CU_WITH_MAPPING, buildTimeBuilder,
-                        clinit.load(configMapping.getKlass().getName()), clinit.load(configMapping.getPrefix()));
-            }
 
             // additional config builders
             ResultHandle configBuilders = clinit.newInstance(AL_NEW);
@@ -468,11 +463,12 @@ public void run() {
                     reinit.invokeStaticMethod(CU_ADD_SOURCE_FACTORY_PROVIDER, buildTimeBuilder,
                             reinit.newInstance(RCSF_NEW, reinit.load(discoveredConfigSourceFactory)));
                 }
-                // add mappings
-                for (ConfigClassWithPrefix configMapping : staticConfigMappings) {
-                    reinit.invokeStaticMethod(CU_WITH_MAPPING, buildTimeBuilder,
-                            reinit.load(configMapping.getKlass().getName()), reinit.load(configMapping.getPrefix()));
+                // additional config builders
+                ResultHandle configBuilders = reinit.newInstance(AL_NEW);
+                for (String configBuilder : staticConfigBuilders) {
+                    reinit.invokeVirtualMethod(AL_ADD, configBuilders, reinit.load(configBuilder));
                 }
+                reinit.invokeStaticMethod(CU_CONFIG_BUILDER_LIST, buildTimeBuilder, configBuilders);
 
                 ResultHandle clinitConfig = reinit.checkCast(reinit.invokeVirtualMethod(SRCB_BUILD, buildTimeBuilder),
                         SmallRyeConfig.class);
@@ -555,12 +551,6 @@ public void run() {
                     readBootstrapConfig.invokeStaticMethod(CU_ADD_SOURCE_FACTORY_PROVIDER, bootstrapBuilder,
                             readBootstrapConfig.newInstance(RCSF_NEW, readBootstrapConfig.load(discoveredConfigSourceFactory)));
                 }
-                // add bootstrap mappings
-                for (ConfigClassWithPrefix configMapping : staticConfigMappings) {
-                    readBootstrapConfig.invokeStaticMethod(CU_WITH_MAPPING, bootstrapBuilder,
-                            readBootstrapConfig.load(configMapping.getKlass().getName()),
-                            readBootstrapConfig.load(configMapping.getPrefix()));
-                }
 
                 // add bootstrap config builders
                 ResultHandle bootstrapConfigBuilders = readBootstrapConfig.newInstance(AL_NEW);
@@ -649,12 +639,6 @@ public void run() {
                         readConfig.newInstance(RCSF_NEW, readConfig.load(discoveredConfigSourceFactory)));
             }
 
-            // add mappings
-            for (ConfigClassWithPrefix configMapping : runtimeConfigMappings) {
-                readConfig.invokeStaticMethod(CU_WITH_MAPPING, runTimeBuilder,
-                        readConfig.load(configMapping.getKlass().getName()), readConfig.load(configMapping.getPrefix()));
-            }
-
             // additional config builders
             ResultHandle configBuilders = readConfig.newInstance(AL_NEW);
             for (String configBuilder : runtimeConfigBuilders) {
diff --git a/core/deployment/src/main/java/io/quarkus/deployment/steps/ConfigGenerationBuildStep.java b/core/deployment/src/main/java/io/quarkus/deployment/steps/ConfigGenerationBuildStep.java
index 111a05329b92f..4a9aa31c796c6 100644
--- a/core/deployment/src/main/java/io/quarkus/deployment/steps/ConfigGenerationBuildStep.java
+++ b/core/deployment/src/main/java/io/quarkus/deployment/steps/ConfigGenerationBuildStep.java
@@ -88,6 +88,10 @@ public class ConfigGenerationBuildStep {
             SmallRyeConfigBuilder.class, "withSources",
             SmallRyeConfigBuilder.class, ConfigSource[].class);
 
+    private static final MethodDescriptor WITH_MAPPING = MethodDescriptor.ofMethod(
+            SmallRyeConfigBuilder.class, "withMapping",
+            SmallRyeConfigBuilder.class, Class.class, String.class);
+
     @BuildStep
     void staticInitSources(
             BuildProducer<StaticInitConfigSourceProviderBuildItem> staticInitConfigSourceProviderBuildItem,
@@ -217,6 +221,33 @@ void extensionMappings(ConfigurationBuildItem configItem,
         }
     }
 
+    @BuildStep
+    void builderMappings(
+            ConfigurationBuildItem configItem,
+            List<ConfigMappingBuildItem> configMappings,
+            BuildProducer<GeneratedClassBuildItem> generatedClass,
+            BuildProducer<ReflectiveClassBuildItem> reflectiveClass,
+            BuildProducer<StaticInitConfigBuilderBuildItem> staticInitConfigBuilder,
+            BuildProducer<RunTimeConfigBuilderBuildItem> runTimeConfigBuilder) {
+
+        // For Static Init Config
+        Set<ConfigClassWithPrefix> staticMappings = new HashSet<>();
+        staticMappings.addAll(staticSafeConfigMappings(configMappings));
+        staticMappings.addAll(configItem.getReadResult().getBuildTimeRunTimeMappings());
+        String staticInitMappingsConfigBuilder = "io.quarkus.runtime.generated.StaticInitMappingsConfigBuilder";
+        generateMappingsConfigBuilder(generatedClass, reflectiveClass, staticInitMappingsConfigBuilder, staticMappings);
+        staticInitConfigBuilder.produce(new StaticInitConfigBuilderBuildItem(staticInitMappingsConfigBuilder));
+
+        // For RunTime Config
+        Set<ConfigClassWithPrefix> runTimeMappings = new HashSet<>();
+        runTimeMappings.addAll(runtimeConfigMappings(configMappings));
+        runTimeMappings.addAll(configItem.getReadResult().getBuildTimeRunTimeMappings());
+        runTimeMappings.addAll(configItem.getReadResult().getRunTimeMappings());
+        String runTimeMappingsConfigBuilder = "io.quarkus.runtime.generated.RunTimeMappingsConfigBuilder";
+        generateMappingsConfigBuilder(generatedClass, reflectiveClass, runTimeMappingsConfigBuilder, runTimeMappings);
+        runTimeConfigBuilder.produce(new RunTimeConfigBuilderBuildItem(runTimeMappingsConfigBuilder));
+    }
+
     /**
      * Generate the Config class that instantiates MP Config and holds all the config objects
      */
@@ -256,6 +287,7 @@ void generateConfigClass(
         staticConfigSourceFactories.addAll(staticInitConfigSourceFactories.stream()
                 .map(StaticInitConfigSourceFactoryBuildItem::getFactoryClassName).collect(Collectors.toSet()));
 
+        // TODO - duplicated now builderMappings. Still required to filter the unknown properties
         Set<ConfigClassWithPrefix> staticMappings = new HashSet<>();
         staticMappings.addAll(staticSafeConfigMappings(configMappings));
         staticMappings.addAll(configItem.getReadResult().getBuildTimeRunTimeMappings());
@@ -484,6 +516,34 @@ private static void generateDefaultsConfigSource(
         reflectiveClass.produce(new ReflectiveClassBuildItem(true, false, false, className));
     }
 
+    private static void generateMappingsConfigBuilder(
+            BuildProducer<GeneratedClassBuildItem> generatedClass,
+            BuildProducer<ReflectiveClassBuildItem> reflectiveClass,
+            String className,
+            Set<ConfigClassWithPrefix> mappings) {
+
+        try (ClassCreator classCreator = ClassCreator.builder()
+                .classOutput(new GeneratedClassGizmoAdaptor(generatedClass, true))
+                .className(className)
+                .interfaces(ConfigBuilder.class)
+                .setFinal(true)
+                .build()) {
+
+            MethodCreator method = classCreator.getMethodCreator(CONFIG_BUILDER);
+            ResultHandle configBuilder = method.getMethodParam(0);
+
+            for (ConfigClassWithPrefix mapping : mappings) {
+                method.invokeVirtualMethod(WITH_MAPPING, configBuilder,
+                        method.loadClass(mapping.getKlass()),
+                        method.load(mapping.getPrefix()));
+            }
+
+            method.returnValue(configBuilder);
+        }
+
+        reflectiveClass.produce(new ReflectiveClassBuildItem(true, false, false, className));
+    }
+
     private static Set<String> discoverService(
             Class<?> serviceClass,
             BuildProducer<ReflectiveClassBuildItem> reflectiveClass) throws IOException {
diff --git a/integration-tests/test-extension/extension/deployment/src/test/java/io/quarkus/config/SecretKeysConfigTest.java b/integration-tests/test-extension/extension/deployment/src/test/java/io/quarkus/config/SecretKeysConfigTest.java
index 120c4c6da57ec..c299b5b3de497 100644
--- a/integration-tests/test-extension/extension/deployment/src/test/java/io/quarkus/config/SecretKeysConfigTest.java
+++ b/integration-tests/test-extension/extension/deployment/src/test/java/io/quarkus/config/SecretKeysConfigTest.java
@@ -39,7 +39,7 @@ void secrets() {
     }
 
     @ConfigMapping(prefix = "secrets.my")
-    interface MappingSecret {
+    public interface MappingSecret {
         String secret();
     }
 }