diff --git a/ft.c b/ft.c
index 4ca1ca6..3ae9ac9 100644
--- a/ft.c
+++ b/ft.c
@@ -457,7 +457,7 @@ static double lastx, lasty;
 
 static int
 outl_moveto(
-	FT_Vector *to,
+	const FT_Vector *to,
 	void *unused
 )
 {
@@ -477,7 +477,7 @@ outl_moveto(
 
 static int
 outl_lineto(
-	FT_Vector *to,
+	const FT_Vector *to,
 	void *unused
 )
 {
@@ -493,8 +493,8 @@ outl_lineto(
 
 static int
 outl_conicto(
-	FT_Vector *control1,
-	FT_Vector *to,
+	const FT_Vector *control1,
+	const FT_Vector *to,
 	void *unused
 )
 {
@@ -514,9 +514,9 @@ outl_conicto(
 
 static int
 outl_cubicto(
-	FT_Vector *control1,
-	FT_Vector *control2,
-	FT_Vector *to,
+	const FT_Vector *control1,
+	const FT_Vector *control2,
+	const FT_Vector *to,
 	void *unused
 )
 {