diff --git a/src/math/lp/dioph_eq.cpp b/src/math/lp/dioph_eq.cpp
index b1c9afe2e..efc313ec6 100644
--- a/src/math/lp/dioph_eq.cpp
+++ b/src/math/lp/dioph_eq.cpp
@@ -4,8 +4,9 @@
 #include "math/lp/lp_utils.h"
 
 namespace lp {
-    struct imp {
-    
+
+    class dioph_eq::imp {
+    public:
         int_solver& lia;
         lar_solver& lra;
 
@@ -13,9 +14,9 @@ namespace lp {
         vector<lar_term> m_e;
             
         void init() {
-            int n_of_rows = lra.r_basis().size();
+            unsigned n_of_rows = static_cast<unsigned>(lra.r_basis().size());
             unsigned skipped = 0;
-            for (unsigned i = 0; i < lra.r_basis().size(); i++) {
+            for (unsigned i = 0; i < n_of_rows; i++) {
                 auto & row = lra.get_row(i);
                 lar_term t;
                 bool is_int = true;
diff --git a/src/math/lp/dioph_eq.h b/src/math/lp/dioph_eq.h
index f37a2baa0..36d45844e 100644
--- a/src/math/lp/dioph_eq.h
+++ b/src/math/lp/dioph_eq.h
@@ -19,9 +19,10 @@ Revision History:
 #include "math/lp/lia_move.h"
 
 namespace lp {
-    struct imp;
+    
     class int_solver;
     class dioph_eq {
+        class imp;
         int_solver& lia;
         imp*        m_imp;
     public:
diff --git a/src/math/lp/int_solver.cpp b/src/math/lp/int_solver.cpp
index aac1caf18..88ac2a1bb 100644
--- a/src/math/lp/int_solver.cpp
+++ b/src/math/lp/int_solver.cpp
@@ -29,7 +29,8 @@ namespace lp {
 
     };
     
-    struct imp {
+    class int_solver::imp {
+        public:
         int_solver&         lia;
         lar_solver&         lra;
         lar_core_solver&    lrac;
diff --git a/src/math/lp/int_solver.h b/src/math/lp/int_solver.h
index 02d6aa519..14d5c8e4e 100644
--- a/src/math/lp/int_solver.h
+++ b/src/math/lp/int_solver.h
@@ -31,16 +31,17 @@ Revision History:
 namespace lp {
 class lar_solver;
 class lar_core_solver;
-struct imp;
 class int_solver {
+
     friend struct create_cut;
     friend class gomory;
     friend class int_cube;
     friend class int_branch;
     friend class int_gcd_test;
     friend class hnf_cutter;
-    friend struct imp;
+    friend class imp;
     friend class dioph_eq;
+    class imp;
     lar_solver&         lra;
     lar_core_solver&    lrac;
     imp*                m_imp;