diff --git a/src/geo/base.js b/src/geo/base.js
index 38180d4b..7e874ebf 100644
--- a/src/geo/base.js
+++ b/src/geo/base.js
@@ -321,12 +321,15 @@
      */
     function circleCenter(A,B,C)
     {
+        let denominator = 2*determinant33([[A.x, A.y, 1], [B.x, B.y, 1], [C.x, C.y, 1]]);
         let xmat = [[A.x*A.x + A.y*A.y, A.y, 1],[B.x*B.x + B.y*B.y, B.y, 1],[C.x*C.x + C.y*C.y, C.y, 1]];
         let ymat = [[A.y, A.x*A.x + A.y*A.y, 1],[B.y, B.x*B.x + B.y*B.y, 1],[C.y, C.x*C.x + C.y*C.y, 1]];
 
-        let center = {x:determinant33(xmat), y:determinant33(ymat), z:A.z};
+        let center = {x:determinant33(xmat)/denominator, y:determinant33(ymat)/denominator, z:A.z};
 
-        return center;
+        if (denominator !== 0) {
+            return center;
+        }
     }
 
     /**