diff --git a/src/cairo-image-surface.c b/src/cairo-image-surface.c
index 441947f6a..c61869a41 100644
--- a/src/cairo-image-surface.c
+++ b/src/cairo-image-surface.c
@@ -36,7 +36,7 @@
 
 #include "cairoint.h"
 
-const cairo_image_surface_t _cairo_image_surface_nil_invalid_format = {
+static const cairo_image_surface_t _cairo_image_surface_nil_invalid_format = {
     {
 	&cairo_image_surface_backend,	/* backend */
 	CAIRO_SURFACE_TYPE_IMAGE,