diff --git a/gtk/Makefile.defaults b/gtk/Makefile.defaults
index dc1203328..51aa02707 100644
--- a/gtk/Makefile.defaults
+++ b/gtk/Makefile.defaults
@@ -25,7 +25,7 @@ NETSURF_USE_ROSPRITE := AUTO
 NETSURF_FS_BACKING_STORE := YES
 
 # Set default GTK version to build for (2 or 3)
-NETSURF_GTK_MAJOR := 2
+NETSURF_GTK_MAJOR ?= 2
 
 # Optimisation levels
 CFLAGS += -O2