diff --git a/src/libslic3r/Fill/FillAdaptive.hpp b/src/libslic3r/Fill/FillAdaptive.hpp
index 4bb80fa06..b24f206da 100644
--- a/src/libslic3r/Fill/FillAdaptive.hpp
+++ b/src/libslic3r/Fill/FillAdaptive.hpp
@@ -8,6 +8,7 @@
 namespace Slic3r {
 
 class PrintObject;
+class TriangleMesh;
 
 namespace FillAdaptive_Internal
 {
diff --git a/src/slic3r/Utils/Process.hpp b/src/slic3r/Utils/Process.hpp
index c6acaa643..65f90222d 100644
--- a/src/slic3r/Utils/Process.hpp
+++ b/src/slic3r/Utils/Process.hpp
@@ -2,6 +2,7 @@
 #define GUI_PROCESS_HPP
 
 class wxWindow;
+class wxString;
 
 namespace Slic3r {
 namespace GUI {