diff --git a/gtk2_ardour/gain_meter.cc b/gtk2_ardour/gain_meter.cc
index f27724d28a..f9677a2e8f 100644
--- a/gtk2_ardour/gain_meter.cc
+++ b/gtk2_ardour/gain_meter.cc
@@ -63,12 +63,6 @@ using namespace std;
 using Gtkmm2ext::Keyboard;
 using namespace ArdourMeter;
 
-#if defined(__APPLE__)
-#define ALT_OPTION (Keyboard::Level4Modifier)
-#elif defined(PLATFORM_WINDOWS)
-#define ALT_OPTION (Keyboard::SecondaryModifier)
-#endif
-
 GainMeter::GainMeter (Session* s, const std::string& layout_script_file)
 	: Gtk::VBox ()
 	, WavesUI (layout_script_file, *this)
@@ -303,7 +297,8 @@ GainMeter::gain_display_button_press (GdkEventButton* ev)
 {
 	switch (ev->type) {
         case GDK_BUTTON_PRESS:
-            if (Keyboard::modifier_state_contains (ev->state, ALT_OPTION)) {
+            /* MOD1 == "Alt" */
+            if (Keyboard::modifier_state_contains (ev->state, GDK_MOD1_MASK)) {
                 _amp->set_gain (dB_to_coefficient(0.0), this);
             }
             break;
@@ -687,7 +682,7 @@ GainMeter::gain_slider_button_press (GdkEventButton* ev)
 {
 	switch (ev->type) {
         case GDK_BUTTON_PRESS:
-            if (Keyboard::modifier_state_contains (ev->state, ALT_OPTION)) {
+            if (Keyboard::modifier_state_contains (ev->state, GDK_MOD1_MASK)) {
                 _amp->set_gain (dB_to_coefficient(0.0), this);
                 return true;
             }