diff --git a/src/particles/elements/RFCavity.H b/src/particles/elements/RFCavity.H
index 41ca1d946..f0337aed3 100644
--- a/src/particles/elements/RFCavity.H
+++ b/src/particles/elements/RFCavity.H
@@ -377,6 +377,14 @@ namespace RFCavityData
                       zlen*sin_data[j]*cos(j*2*pi*z/zlen)/(j*2*pi);
                }
             }
+            else  // endpoint of the RF, outsize zlen
+            {
+               efieldint = std::copysign(z, z)*zmid*0.5_prt*cos_data[0];;
+               for (int j=1; j < m_ncoef; ++j)
+               {
+                 efieldint = efieldint - zlen*sin_data[j]*cos(j*pi)/(j*2*pi);
+               }
+            }
             return std::make_tuple(efield, efieldp, efieldint);
         }