diff --git a/contrib/src/stc/gen_iface.py b/contrib/src/stc/gen_iface.py
index 9a6c188200..4e0afbb129 100644
--- a/contrib/src/stc/gen_iface.py
+++ b/contrib/src/stc/gen_iface.py
@@ -203,6 +203,8 @@ methodOverrideMap = {
         // convert bmp to a xpm in a string
         wxMemoryOutputStream strm;
         wxImage img = bmp.ConvertToImage();
+        if (img.HasAlpha())
+            img.ConvertAlphaToMask();
         img.SaveFile(strm, wxBITMAP_TYPE_XPM);
         size_t len = strm.GetSize();
         char* buff = new char[len+1];
@@ -299,6 +301,8 @@ methodOverrideMap = {
         // convert bmp to a xpm in a string
         wxMemoryOutputStream strm;
         wxImage img = bmp.ConvertToImage();
+        if (img.HasAlpha())
+            img.ConvertAlphaToMask();
         img.SaveFile(strm, wxBITMAP_TYPE_XPM);
         size_t len = strm.GetSize();
         char* buff = new char[len+1];
diff --git a/contrib/src/stc/stc.cpp b/contrib/src/stc/stc.cpp
index 86a9690efb..6f580d7941 100644
--- a/contrib/src/stc/stc.cpp
+++ b/contrib/src/stc/stc.cpp
@@ -517,6 +517,8 @@ void wxStyledTextCtrl::MarkerDefineBitmap(int markerNumber, const wxBitmap& bmp)
         // convert bmp to a xpm in a string
         wxMemoryOutputStream strm;
         wxImage img = bmp.ConvertToImage();
+        if (img.HasAlpha())
+            img.ConvertAlphaToMask();
         img.SaveFile(strm, wxBITMAP_TYPE_XPM);
         size_t len = strm.GetSize();
         char* buff = new char[len+1];
@@ -896,6 +898,8 @@ void wxStyledTextCtrl::RegisterImage(int type, const wxBitmap& bmp) {
         // convert bmp to a xpm in a string
         wxMemoryOutputStream strm;
         wxImage img = bmp.ConvertToImage();
+        if (img.HasAlpha())
+            img.ConvertAlphaToMask();
         img.SaveFile(strm, wxBITMAP_TYPE_XPM);
         size_t len = strm.GetSize();
         char* buff = new char[len+1];
diff --git a/src/stc/gen_iface.py b/src/stc/gen_iface.py
index 9a6c188200..4e0afbb129 100644
--- a/src/stc/gen_iface.py
+++ b/src/stc/gen_iface.py
@@ -203,6 +203,8 @@ methodOverrideMap = {
         // convert bmp to a xpm in a string
         wxMemoryOutputStream strm;
         wxImage img = bmp.ConvertToImage();
+        if (img.HasAlpha())
+            img.ConvertAlphaToMask();
         img.SaveFile(strm, wxBITMAP_TYPE_XPM);
         size_t len = strm.GetSize();
         char* buff = new char[len+1];
@@ -299,6 +301,8 @@ methodOverrideMap = {
         // convert bmp to a xpm in a string
         wxMemoryOutputStream strm;
         wxImage img = bmp.ConvertToImage();
+        if (img.HasAlpha())
+            img.ConvertAlphaToMask();
         img.SaveFile(strm, wxBITMAP_TYPE_XPM);
         size_t len = strm.GetSize();
         char* buff = new char[len+1];
diff --git a/src/stc/stc.cpp b/src/stc/stc.cpp
index 86a9690efb..6f580d7941 100644
--- a/src/stc/stc.cpp
+++ b/src/stc/stc.cpp
@@ -517,6 +517,8 @@ void wxStyledTextCtrl::MarkerDefineBitmap(int markerNumber, const wxBitmap& bmp)
         // convert bmp to a xpm in a string
         wxMemoryOutputStream strm;
         wxImage img = bmp.ConvertToImage();
+        if (img.HasAlpha())
+            img.ConvertAlphaToMask();
         img.SaveFile(strm, wxBITMAP_TYPE_XPM);
         size_t len = strm.GetSize();
         char* buff = new char[len+1];
@@ -896,6 +898,8 @@ void wxStyledTextCtrl::RegisterImage(int type, const wxBitmap& bmp) {
         // convert bmp to a xpm in a string
         wxMemoryOutputStream strm;
         wxImage img = bmp.ConvertToImage();
+        if (img.HasAlpha())
+            img.ConvertAlphaToMask();
         img.SaveFile(strm, wxBITMAP_TYPE_XPM);
         size_t len = strm.GetSize();
         char* buff = new char[len+1];