diff --git a/genaisrc/myai.genai.mts b/genaisrc/myai.genai.mts
index 65742e4b0..0dfb205c9 100644
--- a/genaisrc/myai.genai.mts
+++ b/genaisrc/myai.genai.mts
@@ -199,10 +199,11 @@ export async function invokeLLMOpt(code: string) {
 
         Please modify the original code in <CODE> to ensure that it uses best practices for optimal code execution.
         
+        - do use for loops of the form for (auto const& x : container) { ... } instead of for (it = container.begin(); it != container.end(); ++it) { ... }.
         - do not use assert. Instead use SASSERT.
         - do not change function signatures.
         - do not use std::vector.
-        - do not add new comments.
+        - do not add new comments.        
         - do not split functions into multiple functions.`
         }, {
         system: [],
diff --git a/src/math/lp/lar_core_solver.h b/src/math/lp/lar_core_solver.h
index bd06a17c0..8e727bce9 100644
--- a/src/math/lp/lar_core_solver.h
+++ b/src/math/lp/lar_core_solver.h
@@ -82,9 +82,8 @@ public:
     void backup_x() { m_backup_x = m_r_x; }
 
     void restore_x() {
+        m_r_x = m_backup_x;
         m_r_x.reserve(m_m());
-        for (unsigned i = 0; i < std::min(m_m(), m_backup_x.size()); ++i)
-            m_r_x[i] = m_backup_x[i];
     }
 
     vector<impq> const& r_x() const { return m_r_x; }