diff --git a/src/math/lp/lar_solver.cpp b/src/math/lp/lar_solver.cpp
index 2c127be49..182698cee 100644
--- a/src/math/lp/lar_solver.cpp
+++ b/src/math/lp/lar_solver.cpp
@@ -15,7 +15,7 @@ namespace lp {
         column m_column;
     };
     
-    struct imp {
+    struct lar_solver::imp {
         lar_solver &lra;
         var_register m_var_register;
         svector<column> m_columns;
@@ -51,7 +51,6 @@ namespace lp {
         };
     };
 
-    imp* m_imp;
     lp_settings& lar_solver::settings() { return m_settings; }
 
     lp_settings const& lar_solver::settings() const { return m_settings; }
@@ -188,7 +187,7 @@ namespace lp {
         m_status = s; 
     }
     const u_dependency* lar_solver::crossed_bounds_deps() const { return m_imp->m_crossed_bounds_deps;}
-    u_dependency*& crossed_bounds_deps() { return m_imp->m_crossed_bounds_deps;}
+    u_dependency*& lar_solver::crossed_bounds_deps() { return m_imp->m_crossed_bounds_deps;}
     lpvar lar_solver::crossed_bounds_column() const { return m_imp->m_crossed_bounds_column; }
     lpvar& lar_solver::crossed_bounds_column() { return m_imp->m_crossed_bounds_column; } 
     lpvar lar_solver::local_to_external(lpvar idx) const { return m_imp->m_var_register.local_to_external(idx); }
diff --git a/src/math/lp/lar_solver.h b/src/math/lp/lar_solver.h
index 91195d065..106dc2f42 100644
--- a/src/math/lp/lar_solver.h
+++ b/src/math/lp/lar_solver.h
@@ -47,9 +47,9 @@ namespace lp {
 
 class int_branch;
 class int_solver;
-struct imp;
     
 class lar_solver : public column_namer {
+    struct imp;
     struct term_hasher {
         std::size_t operator()(const lar_term& t) const {
             using std::hash;