diff --git a/src/sat/smt/xor_solver.cpp b/src/sat/smt/xor_solver.cpp
index a605efcb0..5032a1ed7 100644
--- a/src/sat/smt/xor_solver.cpp
+++ b/src/sat/smt/xor_solver.cpp
@@ -769,7 +769,7 @@ namespace xr {
                 ws[j++] = ws[i];
             }
         }
-        ws.shrink(i - j);
+        ws.shrink(j);
     }
     
     // Removes all xor clauses that do not contain any variables