diff --git a/cef3/include/capi/cef_scheme_capi.h b/cef3/include/capi/cef_scheme_capi.h
index f124d745c..c69bb0c3e 100644
--- a/cef3/include/capi/cef_scheme_capi.h
+++ b/cef3/include/capi/cef_scheme_capi.h
@@ -51,11 +51,12 @@ extern "C" {
 // will cause the factory to match all domain names. The |domain_name| value
 // will be ignored for non-standard schemes. If |scheme_name| is a built-in
 // scheme and no handler is returned by |factory| then the built-in scheme
-// handler factory will be called. If |scheme_name| is a custom scheme the
-// CefRegisterCustomScheme() function should be called for that scheme. This
-// function may be called multiple times to change or remove the factory that
-// matches the specified |scheme_name| and optional |domain_name|. Returns false
-// (0) if an error occurs. This function may be called on any thread.
+// handler factory will be called. If |scheme_name| is a custom scheme then also
+// implement the cef_app_t::on_register_custom_schemes() function in all
+// processes. This function may be called multiple times to change or remove the
+// factory that matches the specified |scheme_name| and optional |domain_name|.
+// Returns false (0) if an error occurs. This function may be called on any
+// thread in the browser process.
 ///
 CEF_EXPORT int cef_register_scheme_handler_factory(
     const cef_string_t* scheme_name, const cef_string_t* domain_name,
@@ -63,7 +64,7 @@ CEF_EXPORT int cef_register_scheme_handler_factory(
 
 ///
 // Clear all registered scheme handler factories. Returns false (0) on error.
-// This function may be called on any thread.
+// This function may be called on any thread in the browser process.
 ///
 CEF_EXPORT int cef_clear_scheme_handler_factories();
 
diff --git a/cef3/include/cef_scheme.h b/cef3/include/cef_scheme.h
index a32a3b690..cd8415c07 100644
--- a/cef3/include/cef_scheme.h
+++ b/cef3/include/cef_scheme.h
@@ -54,11 +54,12 @@ class CefSchemeHandlerFactory;
 // will cause the factory to match all domain names. The |domain_name| value
 // will be ignored for non-standard schemes. If |scheme_name| is a built-in
 // scheme and no handler is returned by |factory| then the built-in scheme
-// handler factory will be called. If |scheme_name| is a custom scheme the
-// CefRegisterCustomScheme() function should be called for that scheme.
+// handler factory will be called. If |scheme_name| is a custom scheme then
+// also implement the CefApp::OnRegisterCustomSchemes() method in all processes.
 // This function may be called multiple times to change or remove the factory
 // that matches the specified |scheme_name| and optional |domain_name|.
-// Returns false if an error occurs. This function may be called on any thread.
+// Returns false if an error occurs. This function may be called on any thread
+// in the browser process.
 ///
 /*--cef(optional_param=domain_name,optional_param=factory)--*/
 bool CefRegisterSchemeHandlerFactory(
@@ -68,7 +69,7 @@ bool CefRegisterSchemeHandlerFactory(
 
 ///
 // Clear all registered scheme handler factories. Returns false on error. This
-// function may be called on any thread.
+// function may be called on any thread in the browser process.
 ///
 /*--cef()--*/
 bool CefClearSchemeHandlerFactories();