diff --git a/.travis.yml b/.travis.yml
index 97176338..ad616d2a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -60,6 +60,9 @@ matrix:
       - uname -a
       - whoami
       - sudo apt-get install gpm libgpm-dev libcppunit-dev autoconf-archive
+      # Work around broken certificate of scan.coverity.com
+      - sudo curl -s -L https://entrust.com/root-certificates/entrust_l1k.cer -o /usr/local/share/ca-certificates/entrust_l1k.crt
+      - sudo update-ca-certificates
     script:
       - autoreconf -v --install --force
       - ./configure --prefix=/usr CPPFLAGS="-DDEBUG" CXXFLAGS="-g -O0 -DDEBUG" --with-unit-test
diff --git a/src/fbuttongroup.cpp b/src/fbuttongroup.cpp
index d03f396e..ab892929 100644
--- a/src/fbuttongroup.cpp
+++ b/src/fbuttongroup.cpp
@@ -461,7 +461,7 @@ void FButtonGroup::drawLabel()
 
 // private methods of FButtonGroup
 //----------------------------------------------------------------------
-bool FButtonGroup::isRadioButton (FToggleButton* button) const
+bool FButtonGroup::isRadioButton (const FToggleButton* button) const
 {
   if ( ! button )
     return false;
diff --git a/src/fmenu.cpp b/src/fmenu.cpp
index a95ed734..76d2bac4 100644
--- a/src/fmenu.cpp
+++ b/src/fmenu.cpp
@@ -345,25 +345,25 @@ void FMenu::cb_menuitem_toggled (FWidget* widget, FDataPtr)
 
 // private methods of FMenu
 //----------------------------------------------------------------------
-bool FMenu::isWindowsMenu (FWidget* w) const
+bool FMenu::isWindowsMenu (const FWidget* w) const
 {
   return w->isDialogWidget();
 }
 
 //----------------------------------------------------------------------
-bool FMenu::isMenuBar (FWidget* w) const
+bool FMenu::isMenuBar (const FWidget* w) const
 {
   return w->isInstanceOf("FMenuBar");
 }
 
 //----------------------------------------------------------------------
-bool FMenu::isMenu (FWidget* w) const
+bool FMenu::isMenu (const FWidget* w) const
 {
   return w->isInstanceOf("FMenu");
 }
 
 //----------------------------------------------------------------------
-bool FMenu::isRadioMenuItem (FWidget* w) const
+bool FMenu::isRadioMenuItem (const FWidget* w) const
 {
   return w->isInstanceOf("FRadioMenuItem");
 }
diff --git a/src/fobject.cpp b/src/fobject.cpp
index 9d9fc352..b9da7b89 100644
--- a/src/fobject.cpp
+++ b/src/fobject.cpp
@@ -113,7 +113,7 @@ FObject* FObject::getChild (int index) const
 }
 
 //----------------------------------------------------------------------
-bool FObject::isChild (FObject* obj) const
+bool FObject::isChild (const FObject* obj) const
 {
   // Find out if obj is a child object of mine
 
diff --git a/src/include/final/fbuttongroup.h b/src/include/final/fbuttongroup.h
index a5b91de3..7d50c92b 100644
--- a/src/include/final/fbuttongroup.h
+++ b/src/include/final/fbuttongroup.h
@@ -129,7 +129,7 @@ class FButtonGroup : public FScrollView
     static constexpr std::size_t NOT_SET = static_cast<std::size_t>(-1);
 
     // Inquiries
-    bool                isRadioButton (FToggleButton*) const;
+    bool                isRadioButton (const FToggleButton*) const;
 
     // Methods
     void                init();
diff --git a/src/include/final/fmenu.h b/src/include/final/fmenu.h
index 49917e80..5f5f8da7 100644
--- a/src/include/final/fmenu.h
+++ b/src/include/final/fmenu.h
@@ -161,10 +161,10 @@ class FMenu : public FWindow, public FMenuList
     void         setSuperMenu (FWidget*);
 
     // Inquiries
-    bool         isWindowsMenu (FWidget*) const;
-    bool         isMenuBar (FWidget*) const;
-    bool         isMenu (FWidget*) const;
-    bool         isRadioMenuItem (FWidget*) const;
+    bool         isWindowsMenu (const FWidget*) const;
+    bool         isMenuBar (const FWidget*) const;
+    bool         isMenu (const FWidget*) const;
+    bool         isRadioMenuItem (const FWidget*) const;
     bool         isSubMenu() const;
     bool         isMouseOverMenu (const FPoint&);
     bool         isMouseOverSubMenu (const FPoint&);
diff --git a/src/include/final/fmenubar.h b/src/include/final/fmenubar.h
index 41c5b35b..144bf90c 100644
--- a/src/include/final/fmenubar.h
+++ b/src/include/final/fmenubar.h
@@ -121,7 +121,7 @@ class FMenuBar : public FWindow, public FMenuList
     } menuText;
 
     // Inquiry
-    bool         isMenu (FMenuItem*) const;
+    bool         isMenu (const FMenuItem*) const;
 
     // Methods
     void         init();
@@ -168,7 +168,7 @@ inline const char* FMenuBar::getClassName() const
 { return "FMenuBar"; }
 
 //----------------------------------------------------------------------
-inline bool FMenuBar::isMenu (FMenuItem* mi) const
+inline bool FMenuBar::isMenu (const FMenuItem* mi) const
 { return mi->hasMenu(); }
 
 }  // namespace finalcut
diff --git a/src/include/final/fobject.h b/src/include/final/fobject.h
index 39b7db61..ca93937c 100644
--- a/src/include/final/fobject.h
+++ b/src/include/final/fobject.h
@@ -98,8 +98,8 @@ class FObject
     // Inquiries
     bool                 hasParent() const;
     bool                 hasChildren() const;
-    bool                 isChild (FObject*) const;
-    bool                 isDirectChild (FObject*) const;
+    bool                 isChild (const FObject*) const;
+    bool                 isDirectChild (const FObject*) const;
     bool                 isWidget() const;
     bool                 isInstanceOf (const char[]) const;
     bool                 isTimerInUpdating() const;
@@ -205,7 +205,7 @@ inline bool FObject::hasChildren() const
 { return bool( ! children_list.empty() ); }
 
 //----------------------------------------------------------------------
-inline bool FObject::isDirectChild (FObject* obj) const
+inline bool FObject::isDirectChild (const FObject* obj) const
 { return bool( obj->getParent() == this ); }
 
 //----------------------------------------------------------------------