diff --git a/configure b/configure
index ebda4c60ff54..fdaff113501f 100755
--- a/configure
+++ b/configure
@@ -3288,6 +3288,7 @@ EOF
 		;;
 	haiku*)
 		append_var DEFINES "-DSYSTEM_NOT_SUPPORTING_D_TYPE"
+		append_var DEFINES "-D_GNU_SOURCE"
 		# Needs -lnetwork for the timidity MIDI driver
 		append_var LIBS "-lnetwork"
 		_seq_midi=no