diff --git a/generators/poppler/formfields.h b/generators/poppler/formfields.h
--- a/generators/poppler/formfields.h
+++ b/generators/poppler/formfields.h
@@ -12,6 +12,7 @@
 
 #include <poppler-form.h>
 #include "core/form.h"
+#include <config-okular-poppler.h>
 
 class PopplerFormFieldButton : public Okular::FormFieldButton
 {
@@ -111,6 +112,7 @@
 
 };
 
+#ifdef HAVE_POPPLER_0_51
 class PopplerSignatureInfo;
 class PopplerFormFieldSignature : public Okular::FormFieldSignature
 {
@@ -136,5 +138,6 @@
         Okular::NormalizedRect m_rect;
         int m_id;
 };
+#endif
 
 #endif
diff --git a/generators/poppler/formfields.cpp b/generators/poppler/formfields.cpp
--- a/generators/poppler/formfields.cpp
+++ b/generators/poppler/formfields.cpp
@@ -16,8 +16,6 @@
 
 #include <poppler-qt5.h>
 
-#include <config-okular-poppler.h>
-
 extern Okular::Action* createLinkFromPopplerLink(const Poppler::Link *popplerLink, bool deletePopplerLink = true);
 #ifdef HAVE_POPPLER_0_65
 # define SET_ANNOT_ACTIONS \
@@ -369,25 +367,13 @@
     return m_field->canBeSpellChecked();
 }
 
-#ifndef HAVE_POPPLER_0_51
-
-class DummySignatureInfo : public Okular::SignatureInfo
-{
-};
-
-#endif
-
-
+#ifdef HAVE_POPPLER_0_51
 PopplerFormFieldSignature::PopplerFormFieldSignature( Poppler::FormFieldSignature * field )
     : Okular::FormFieldSignature(), m_field( field )
 {
     m_rect = Okular::NormalizedRect::fromQRectF( m_field->rect() );
     m_id = m_field->id();
-#ifdef HAVE_POPPLER_0_51
     m_info = new PopplerSignatureInfo( m_field->validate( Poppler::FormFieldSignature::ValidateVerifyCertificate ) );
-#else
-    m_info = new DummySignatureInfo();
-#endif
     SET_ACTIONS
 }
 
@@ -450,3 +436,4 @@
 {
     return *m_info;
 }
+#endif
diff --git a/generators/poppler/generator_pdf.cpp b/generators/poppler/generator_pdf.cpp
--- a/generators/poppler/generator_pdf.cpp
+++ b/generators/poppler/generator_pdf.cpp
@@ -523,9 +523,11 @@
         }
         break;
 #endif
-        
+
+#ifdef HAVE_POPPLER_0_50
         case Poppler::Link::OCGState:
             Q_UNREACHABLE();
+#endif
     }
 
 #ifdef HAVE_POPPLER_0_64
@@ -1974,10 +1976,12 @@
             case Poppler::FormField::FormChoice:
                 of = new PopplerFormFieldChoice( static_cast<Poppler::FormFieldChoice*>( f ) );
                 break;
+#ifdef HAVE_POPPLER_0_51
             case Poppler::FormField::FormSignature: {
                 of = new PopplerFormFieldSignature( static_cast<Poppler::FormFieldSignature*>( f ) );
                 break;
             }
+#endif
             default: ;
         }
         if ( of )