diff --git a/src/ClpModel.hpp b/src/ClpModel.hpp
index 6115e18e..cbc6007d 100644
--- a/src/ClpModel.hpp
+++ b/src/ClpModel.hpp
@@ -247,6 +247,8 @@ class CLPLIB_EXPORT ClpModel {
     bool keepZero = false)
   {
     matrix_->modifyCoefficient(row, column, newElement, keepZero);
+    // Say matrix changed
+    whatsChanged_ &= ~15;
   }
   /** Change row lower bounds */
   void chgRowLower(const double *rowLower);