diff --git a/modules/mol/alg/src/accessibility.cc b/modules/mol/alg/src/accessibility.cc
index a1becdd7f83c3de0b939e22788d6bf4bb3f22926..276b53ba2256802e9c9afc52c2f4b49e308e796f 100644
--- a/modules/mol/alg/src/accessibility.cc
+++ b/modules/mol/alg/src/accessibility.cc
@@ -203,6 +203,11 @@ Real GetAtomAccessibilityNACCESS(Real x_pos, Real y_pos, Real z_pos,
     Real a = x_pos - x[i];
     Real b = y_pos - y[i];  
     Real c = a*a + b*b;
+
+    if(c == Real(0.0)) {
+      return 0.0;
+    }
+
     dx[i] = a;
     dy[i] = b;
     dsqr[i] = c;