diff --git a/core-common/src/main/java/org/mapstruct/Qualifier.java b/core-common/src/main/java/org/mapstruct/Qualifier.java
index fdaaad1e3..9a5406b9e 100644
--- a/core-common/src/main/java/org/mapstruct/Qualifier.java
+++ b/core-common/src/main/java/org/mapstruct/Qualifier.java
@@ -44,6 +44,8 @@ import java.lang.annotation.Target;
  * }
  * </pre>
  *
+ * <b>NOTE: </b>Qualifiers should have {@link RetentionPolicy#CLASS}.
+ *
  * @author Sjaak Derksen
  */
 @Target(ElementType.ANNOTATION_TYPE)
diff --git a/documentation/src/main/asciidoc/mapstruct-reference-guide.asciidoc b/documentation/src/main/asciidoc/mapstruct-reference-guide.asciidoc
index f545113af..24b81e34c 100644
--- a/documentation/src/main/asciidoc/mapstruct-reference-guide.asciidoc
+++ b/documentation/src/main/asciidoc/mapstruct-reference-guide.asciidoc
@@ -865,6 +865,11 @@ public class Titles {
 ----
 ====
 
+[WARNING]
+====
+Please make sure the used retention policy equals retention policy `CLASS` (`@Retention(RetentionPolicy.CLASS)`).
+====
+
 [WARNING]
 ====
 A class / method annotated with a qualifier will not qualify anymore for mappings that do not have the `qualifiedBy` element.