diff --git a/include/geos/algorithm/construct/MaximumInscribedCircle.h b/include/geos/algorithm/construct/MaximumInscribedCircle.h
index f19a954f1..af4260c49 100644
--- a/include/geos/algorithm/construct/MaximumInscribedCircle.h
+++ b/include/geos/algorithm/construct/MaximumInscribedCircle.h
@@ -136,7 +136,7 @@ class GEOS_DLL MaximumInscribedCircle {
     geom::CoordinateXY radiusPt;
 
     /* private methods */
-    double distanceToBoundary(geom::Point& pt);
+    double distanceToBoundary(const geom::Point& pt);
     double distanceToBoundary(double x, double y);
     void compute();
 
diff --git a/src/algorithm/construct/MaximumInscribedCircle.cpp b/src/algorithm/construct/MaximumInscribedCircle.cpp
index 7dc85b8c6..a8f83d1be 100644
--- a/src/algorithm/construct/MaximumInscribedCircle.cpp
+++ b/src/algorithm/construct/MaximumInscribedCircle.cpp
@@ -152,7 +152,7 @@ MaximumInscribedCircle::distanceToBoundary(double x, double y)
 
 /* private */
 double
-MaximumInscribedCircle::distanceToBoundary(Point& pt)
+MaximumInscribedCircle::distanceToBoundary(const Point& pt)
 {
     double dist = indexedDistance.distance(&pt);
     // double dist = inputGeomBoundary->distance(pt.get());