diff --git a/modules/calib3d/src/calibinit.cpp b/modules/calib3d/src/calibinit.cpp
index c979f0bb62..e4909bb575 100644
--- a/modules/calib3d/src/calibinit.cpp
+++ b/modules/calib3d/src/calibinit.cpp
@@ -1630,7 +1630,7 @@ void ChessBoardDetector::findQuadNeighbors()
                     {
                         // check edge lengths, make sure they're compatible
                         // edges that are different by more than 1:4 are rejected
-                        float ediff = cur_quad.edge_len - q_k.edge_len;
+                        const float ediff = fabs(cur_quad.edge_len - q_k.edge_len);
                         if (ediff > 32*cur_quad.edge_len ||
                             ediff > 32*q_k.edge_len)
                         {