diff --git a/qt5/src/poppler-form.h b/qt5/src/poppler-form.h
index 401d79c..7996a2c 100644
--- a/qt5/src/poppler-form.h
+++ b/qt5/src/poppler-form.h
@@ -350,7 +350,7 @@
     /**
       A signature validation info helper class.
 
-      \since xy.z
+      \since 0.51
      */
     class SignatureValidationInfoPrivate;
     class POPPLER_QT5_EXPORT SignatureValidationInfo {
@@ -419,7 +419,7 @@
     /**
       A form field that represents a signature.
 
-      \since xy.z
+      \since 0.51
      */
     class POPPLER_QT5_EXPORT FormFieldSignature : public FormField {
     public: