diff --git a/interface/wx/sysopt.h b/interface/wx/sysopt.h
index 2b595766dc..2eef48cd48 100644
--- a/interface/wx/sysopt.h
+++ b/interface/wx/sysopt.h
@@ -14,6 +14,18 @@
     used to optimize behaviour that doesn't deserve a distinct API,
     but is still important to be able to configure.
 
+    System options can be set by the program itself using SetOption() method
+    and they also can be set from the program environment by defining an
+    environment variable @c wx_option to set the given option for all wxWidgets
+    applications or @c wx_appname_option to set it just for the application
+    with the given name (as returned by wxApp::GetAppName()). Notice that any
+    characters not allowed in the environment variables names, such as periods
+    and dashes, should be replaced with underscores. E.g. to define a system
+    option "foo-bar" you need to define the environment variable "wx_foo_bar".
+
+    The program may use system options for its own needs but they are mostly
+    used to control the behaviour of wxWidgets library itself.
+
     These options are currently recognised by wxWidgets:
 
 
diff --git a/src/common/sysopt.cpp b/src/common/sysopt.cpp
index c9834763be..2f611918dd 100644
--- a/src/common/sysopt.cpp
+++ b/src/common/sysopt.cpp
@@ -83,6 +83,7 @@ wxString wxSystemOptions::GetOption(const wxString& name)
         // and then for "wx_name" which can be set to change the option globally
         wxString var(name);
         var.Replace(wxT("."), wxT("_"));  // '.'s not allowed in env var names
+        var.Replace(wxT("-"), wxT("_"));  // and neither are '-'s
 
         wxString appname;
         if ( wxTheApp )