diff --git a/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/AbstractConfigListener.java b/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/AbstractConfigListener.java
index 4eb92d7e84277..6e99c7e9b3be1 100644
--- a/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/AbstractConfigListener.java
+++ b/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/AbstractConfigListener.java
@@ -14,6 +14,8 @@
 import io.quarkus.annotation.processor.documentation.config.discovery.EnumDefinition;
 import io.quarkus.annotation.processor.documentation.config.discovery.EnumDefinition.EnumConstant;
 import io.quarkus.annotation.processor.documentation.config.discovery.ResolvedType;
+import io.quarkus.annotation.processor.documentation.config.model.ConfigPhase;
+import io.quarkus.annotation.processor.documentation.config.model.ExtensionModule;
 import io.quarkus.annotation.processor.documentation.config.util.Types;
 import io.quarkus.annotation.processor.util.Config;
 import io.quarkus.annotation.processor.util.Utils;
@@ -66,6 +68,18 @@ public void onResolvedEnum(TypeElement enumTypeElement) {
         configCollector.addResolvedEnum(enumDefinition);
     }
 
+    protected void validateRuntimeConfigOnDeploymentModules(ConfigPhase configPhase, TypeElement configRoot) {
+        if (configPhase.equals(ConfigPhase.RUN_TIME) || configPhase.equals(ConfigPhase.BUILD_AND_RUN_TIME_FIXED)) {
+            ExtensionModule.ExtensionModuleType type = config.getExtensionModule().type();
+            if (type.equals(ExtensionModule.ExtensionModuleType.DEPLOYMENT)) {
+                throw new IllegalStateException(String.format(
+                        "Error on %s: Configuration classes with ConfigPhase.RUN_TIME or " +
+                                "ConfigPhase.BUILD_AND_RUNTIME_FIXED phases, must reside in the respective module.",
+                        configRoot.getSimpleName().toString()));
+            }
+        }
+    }
+
     protected void handleCommonPropertyAnnotations(DiscoveryConfigProperty.Builder builder,
             Map<String, AnnotationMirror> propertyAnnotations, ResolvedType resolvedType, String sourceElementName) {
 
diff --git a/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/ConfigMappingListener.java b/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/ConfigMappingListener.java
index cda99142c602e..ea4135f7adfe3 100644
--- a/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/ConfigMappingListener.java
+++ b/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/ConfigMappingListener.java
@@ -75,6 +75,8 @@ public Optional<DiscoveryConfigRoot> onConfigRoot(TypeElement configRoot) {
             }
         }
 
+        validateRuntimeConfigOnDeploymentModules(configPhase, configRoot);
+
         for (Map.Entry<? extends ExecutableElement, ? extends AnnotationValue> entry : configMappingAnnotion.getElementValues()
                 .entrySet()) {
             if ("prefix()".equals(entry.getKey().toString())) {
diff --git a/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/LegacyConfigRootListener.java b/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/LegacyConfigRootListener.java
index 2410b8c62b9d6..f675f902fc9fe 100644
--- a/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/LegacyConfigRootListener.java
+++ b/core/processor/src/main/java/io/quarkus/annotation/processor/documentation/config/scanner/LegacyConfigRootListener.java
@@ -79,6 +79,8 @@ public Optional<DiscoveryConfigRoot> onConfigRoot(TypeElement configRoot) {
             }
         }
 
+        validateRuntimeConfigOnDeploymentModules(configPhase, configRoot);
+
         String overriddenDocPrefix = null;
         if (configDocPrefixAnnotation != null) {
             for (Map.Entry<? extends ExecutableElement, ? extends AnnotationValue> entry : configDocPrefixAnnotation