diff --git a/gtk2_ardour/SConscript b/gtk2_ardour/SConscript
index ac58fe3f24..53576302cf 100644
--- a/gtk2_ardour/SConscript
+++ b/gtk2_ardour/SConscript
@@ -51,6 +51,7 @@ gtkardour.Merge ([
 
 if gtkardour['FFT_ANALYSIS']:
 	gtkardour.Merge ([libraries['fftw3f']])
+	gtkardour.Append(CCFLAGS='-DFFT_ANALYSIS')
 
 if gtkardour['VST']:
     gtkardour.Merge ([ libraries['fst']])