diff --git a/src/bezier2.h b/src/bezier2.h
index 9dff6c3..436ca3f 100644
--- a/src/bezier2.h
+++ b/src/bezier2.h
@@ -30,11 +30,11 @@ typedef struct Bezier2f_s {
 Bezier2 Bezier2_CreateLinear(double x0, double y0, double x1, double y1);
 Bezier2 Bezier2_CreateQuadratic(double x0, double y0, double x1, double y1, double x2, double y2);
 Bezier2 Bezier2_CreateCubic(double x0, double y0, double x1, double y1, double x2, double y2, double x3, double y3);
-Point2 Bezier2_Get(Bezier2* this, double t);
+Point2 Bezier2_Get(const Bezier2* this, double t);
 
 Bezier2f Bezier2f_CreateLinear(float x0, float y0, float x1, float y1);
 Bezier2f Bezier2f_CreateQuadratic(float x0, float y0, float x1, float y1, float x2, float y2);
 Bezier2f Bezier2f_CreateCubic(float x0, float y0, float x1, float y1, float x2, float y2, float x3, float y3);
-Point2f Bezier2f_Get(Bezier2f* this, float t);
+Point2f Bezier2f_Get(const Bezier2f* this, float t);
 
 #endif // __HMAH_BEZIER2_H__
diff --git a/src/bezier3.h b/src/bezier3.h
index 6e0f814..d1eeeda 100644
--- a/src/bezier3.h
+++ b/src/bezier3.h
@@ -32,11 +32,11 @@ typedef struct Bezier3f_s {
 Bezier3 Bezier3_CreateLinear(double x0, double y0, double z0, double x1, double y1, double z1);
 Bezier3 Bezier3_CreateQuadratic(double x0, double y0, double z0, double x1, double y1, double z1, double x2, double y2, double z2);
 Bezier3 Bezier3_CreateCubic(double x0, double y0, double z0, double x1, double y1, double z1, double x2, double y2, double z2, double x3, double y3, double z3);
-Point3 Bezier3_Get(Bezier3* this, double t);
+Point3 Bezier3_Get(const Bezier3* this, double t);
 
 Bezier3f Bezier3f_CreateLinear(float x0, float y0, float z0, float x1, float y1, float z1);
 Bezier3f Bezier3f_CreateQuadratic(float x0, float y0, float z0, float x1, float y1, float z1, float x2, float y2, float z2);
 Bezier3f Bezier3f_CreateCubic(float x0, float y0, float z0, float x1, float y1, float z1, float x2, float y2, float z2, float x3, float y3, float z3);
-Point3f Bezier3f_Get(Bezier3f* this, float t);
+Point3f Bezier3f_Get(const Bezier3f* this, float t);
 
 #endif // __HMAH_BEZIER3_H_
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