diff --git a/src/cairo-bentley-ottmann.c b/src/cairo-bentley-ottmann.c
index 2011e73bd..eb4cee430 100644
--- a/src/cairo-bentley-ottmann.c
+++ b/src/cairo-bentley-ottmann.c
@@ -368,7 +368,7 @@ _cairo_bo_sweep_line_compare_edges (const cairo_bo_sweep_line_t	*sweep_line,
 {
     int cmp;
 
-    cmp = cairo_lines_compare_at_y (&a->edge.line,
+    cmp = _cairo_lines_compare_at_y (&a->edge.line,
 				    &b->edge.line,
 				    sweep_line->current_y);
     if (cmp)
diff --git a/src/cairo-line-private.h b/src/cairo-line-private.h
index 08bf4b358..6ddcae18d 100644
--- a/src/cairo-line-private.h
+++ b/src/cairo-line-private.h
@@ -42,7 +42,7 @@
 CAIRO_BEGIN_DECLS
 
 cairo_private int
-cairo_lines_compare_at_y(const cairo_line_t *a,
+_cairo_lines_compare_at_y (const cairo_line_t *a,
 			 const cairo_line_t *b,
 			 int y);
 
diff --git a/src/cairo-line.c b/src/cairo-line.c
index dc00a9cb1..2c1768eeb 100644
--- a/src/cairo-line.c
+++ b/src/cairo-line.c
@@ -278,7 +278,8 @@ static int bbox_compare (const cairo_line_t *a,
     return 0;
 }
 
-int cairo_lines_compare_at_y (const cairo_line_t *a,
+int
+_cairo_lines_compare_at_y (const cairo_line_t *a,
 			      const cairo_line_t *b,
 			      int y)
 {
diff --git a/src/cairo-traps.c b/src/cairo-traps.c
index c54f6f2ef..b59b96d43 100644
--- a/src/cairo-traps.c
+++ b/src/cairo-traps.c
@@ -404,7 +404,7 @@ static void add_tri (cairo_traps_t *traps,
 	y2 = tmp;
     }
 
-    if (cairo_lines_compare_at_y (left, right, y1) > 0) {
+    if (_cairo_lines_compare_at_y (left, right, y1) > 0) {
 	const cairo_line_t *tmp = left;
 	left = right;
 	right = tmp;