diff --git a/src/sat/kissat/VERSION b/src/sat/kissat/VERSION
new file mode 100644
index 0000000000..4d54daddb6
--- /dev/null
+++ b/src/sat/kissat/VERSION
@@ -0,0 +1 @@
+4.0.2
diff --git a/src/sat/kissat/check.c b/src/sat/kissat/check.c
index fa771f2c75..e4b7988da0 100644
--- a/src/sat/kissat/check.c
+++ b/src/sat/kissat/check.c
@@ -16,6 +16,8 @@
 #undef LOGPREFIX
 #define LOGPREFIX "CHECK"
 
+ABC_NAMESPACE_IMPL_START
+
 void kissat_check_satisfying_assignment (kissat *solver) {
   LOG ("checking satisfying assignment");
   const int *const begin = BEGIN_STACK (solver->original);
@@ -51,16 +53,20 @@ void kissat_check_satisfying_assignment (kissat *solver) {
   LOG ("assignment satisfies all %zu original clauses", count);
 }
 
+ABC_NAMESPACE_IMPL_END
+
 #include "allocate.h"
 #include "inline.h"
 #include "sort.h"
 
+ABC_NAMESPACE_IMPL_START
+
 typedef struct hash hash;
 typedef struct bucket bucket;
 
 // clang-format off
 
-typedef STACK (bucket*) buckets;
+typedef STACK (bucket*) buckets_;
 
 // clang-format on
 
@@ -82,7 +88,7 @@ struct checker {
 
   bucket **table;
 
-  buckets *watches;
+  buckets_ *watches;
   bool *marks;
   bool *large;
   bool *used;
@@ -151,7 +157,7 @@ static void init_nonces (kissat *solver, checker *checker) {
 
 void kissat_init_checker (kissat *solver) {
   LOG ("initializing internal proof checker");
-  checker *checker = kissat_calloc (solver, 1, sizeof (struct checker));
+  checker *checker = (struct checker*)kissat_calloc (solver, 1, sizeof (struct checker));
   solver->checker = checker;
   init_nonces (solver, checker);
 }
@@ -172,7 +178,7 @@ static void release_watches (kissat *solver, checker *checker) {
   for (unsigned i = 0; i < lits; i++)
     RELEASE_STACK (checker->watches[i]);
   kissat_dealloc (solver, checker->watches, 2 * checker->size,
-                  sizeof (buckets));
+                  sizeof (buckets_));
 }
 
 void kissat_release_checker (kissat *solver) {
@@ -191,8 +197,12 @@ void kissat_release_checker (kissat *solver) {
 
 #ifndef KISSAT_QUIET
 
+ABC_NAMESPACE_IMPL_END
+
 #include <inttypes.h>
 
+ABC_NAMESPACE_IMPL_START
+
 #define PERCENT_ADDED(NAME) kissat_percent (checker->NAME, checker->added)
 #define PERCENT_CHECKED(NAME) \
   kissat_percent (checker->NAME, checker->checked)
@@ -249,7 +259,7 @@ static void resize_hash (kissat *solver, checker *checker) {
   const unsigned old_hashed = checker->hashed;
   KISSAT_assert (old_hashed < MAX_SIZE);
   const unsigned new_hashed = old_hashed ? 2 * old_hashed : 1;
-  bucket **table = kissat_calloc (solver, new_hashed, sizeof (bucket *));
+  bucket **table = (bucket**) kissat_calloc (solver, new_hashed, sizeof (bucket *));
   bucket **old_table = checker->table;
   for (unsigned i = 0; i < old_hashed; i++) {
     for (bucket *bucket = old_table[i], *next; bucket; bucket = next) {
@@ -303,7 +313,7 @@ static void checker_assign (kissat *solver, checker *checker, unsigned lit,
   PUSH_STACK (checker->trail, lit);
 }
 
-static buckets *checker_watches (checker *checker, unsigned lit) {
+static buckets_ *checker_watches (checker *checker, unsigned lit) {
   KISSAT_assert (VALID_CHECKER_LIT (lit));
   return checker->watches + lit;
 }
@@ -311,14 +321,14 @@ static buckets *checker_watches (checker *checker, unsigned lit) {
 static void watch_checker_literal (kissat *solver, checker *checker,
                                    bucket *bucket, unsigned lit) {
   LOGLINE3 ("checker watches %u in", lit);
-  buckets *buckets = checker_watches (checker, lit);
+  buckets_ *buckets = checker_watches (checker, lit);
   PUSH_STACK (*buckets, bucket);
 }
 
 static void unwatch_checker_literal (kissat *solver, checker *checker,
                                      bucket *bucket, unsigned lit) {
   LOGLINE3 ("checker unwatches %u in", lit);
-  buckets *buckets = checker_watches (checker, lit);
+  buckets_ *buckets = checker_watches (checker, lit);
   REMOVE_STACK (struct bucket *, *buckets, bucket);
 #ifndef LOGGING
   (void) solver;
@@ -535,15 +545,15 @@ static void resize_checker (kissat *solver, checker *checker,
     LOG3 ("resizing checker form %u to %u", size, new_size);
     const unsigned size2 = 2 * size;
     const unsigned new_size2 = 2 * new_size;
-    checker->marks = kissat_realloc (solver, checker->marks, size2,
+    checker->marks = (bool*)kissat_realloc (solver, checker->marks, size2,
                                      new_size2 * sizeof (bool));
-    checker->used = kissat_realloc (solver, checker->used, size2,
+    checker->used = (bool*)kissat_realloc (solver, checker->used, size2,
                                     new_size2 * sizeof (bool));
-    checker->large = kissat_realloc (solver, checker->large, size2,
+    checker->large = (bool*)kissat_realloc (solver, checker->large, size2,
                                      new_size2 * sizeof (bool));
     checker->values =
-        kissat_realloc (solver, checker->values, size2, new_size2);
-    checker->watches = kissat_realloc (
+      (signed char *)kissat_realloc (solver, checker->values, size2, new_size2);
+    checker->watches = (buckets_*)kissat_realloc (
         solver, checker->watches, size2 * sizeof *checker->watches,
         new_size2 * sizeof *checker->watches);
     checker->size = new_size;
@@ -685,7 +695,7 @@ static bool checker_propagate (kissat *solver, checker *checker) {
     KISSAT_assert (values[lit] > 0);
     KISSAT_assert (values[not_lit] < 0);
     propagated++;
-    buckets *buckets = checker_watches (checker, not_lit);
+    buckets_ *buckets = checker_watches (checker, not_lit);
     bucket **begin_of_lines = BEGIN_STACK (*buckets), **q = begin_of_lines;
     bucket *const *end_of_lines = END_STACK (*buckets), *const *p = q;
     while (p != end_of_lines) {
@@ -793,7 +803,7 @@ static bool checker_blocked_literal (kissat *solver, checker *checker,
   const unsigned not_lit = lit ^ 1;
   if (checker->large[not_lit])
     return false;
-  buckets *buckets = checker_watches (checker, not_lit);
+  buckets_ *buckets = checker_watches (checker, not_lit);
   bucket *const *const begin_of_lines = BEGIN_STACK (*buckets);
   bucket *const *const end_of_lines = END_STACK (*buckets);
   bucket *const *p = begin_of_lines;
@@ -1030,6 +1040,11 @@ void dump_checker (kissat *solver) {
       dump_line (bucket);
 }
 
+ABC_NAMESPACE_IMPL_END
+
 #else
+ABC_NAMESPACE_IMPL_START
 int kissat_check_dummy_to_avoid_warning;
+ABC_NAMESPACE_IMPL_END
 #endif
+
diff --git a/src/sat/kissat/definition.c b/src/sat/kissat/definition.c
index 75db5b8f50..a444ef5165 100644
--- a/src/sat/kissat/definition.c
+++ b/src/sat/kissat/definition.c
@@ -57,7 +57,7 @@ static void traverse_one_sided_core_lemma (void *state, bool learned,
                                            const unsigned *lits) {
   if (!learned)
     return;
-  lemma_extractor *extractor = state;
+  lemma_extractor *extractor = (lemma_extractor*)state;
   kissat *solver = extractor->solver;
   const unsigned unit = extractor->unit;
   unsigneds *added = &solver->added;
diff --git a/src/sat/kissat/dump.c b/src/sat/kissat/dump.c
index c1b2796d30..104ca2e473 100644
--- a/src/sat/kissat/dump.c
+++ b/src/sat/kissat/dump.c
@@ -6,6 +6,8 @@
 
 #include <inttypes.h>
 
+ABC_NAMESPACE_IMPL_START
+
 static void dump_literal (kissat *solver, unsigned ilit) {
   const int elit = kissat_export_literal (solver, ilit);
   printf ("%u(%d)", ilit, elit);
@@ -279,17 +281,21 @@ int kissat_dump (kissat *solver) {
   else
     dump_queue (solver);
   dump_values (solver);
-  printf ("binary = %" PRIu64 "\n", solver->statistics.clauses_binary);
+  printf ("binary = %" PRIu64 "\n", solver->statistics_.clauses_binary);
   printf ("irredundant = %" PRIu64 "\n",
-          solver->statistics.clauses_irredundant);
+          solver->statistics_.clauses_irredundant);
   printf ("redundant = %" PRIu64 "\n",
-          solver->statistics.clauses_redundant);
+          solver->statistics_.clauses_redundant);
   dump_binaries (solver);
   dump_clauses (solver);
   dump_extend (solver);
   return 0;
 }
 
+ABC_NAMESPACE_IMPL_END
+
 #else
+ABC_NAMESPACE_IMPL_START
 int kissat_dump_dummy_to_avoid_warning;
+ABC_NAMESPACE_IMPL_END
 #endif
diff --git a/src/sat/kissat/global.h b/src/sat/kissat/global.h
index e6c20bc055..bf9c030da0 100644
--- a/src/sat/kissat/global.h
+++ b/src/sat/kissat/global.h
@@ -1,13 +1,19 @@
 #ifndef ABC_SAT_KISSAT_GLOBAL_H_
 #define ABC_SAT_KISSAT_GLOBAL_H_
 
-#define KISSAT_COMPACT
+// comment out next line to enable kissat debug mode
 #define KISSAT_NDEBUG
+
+#define KISSAT_COMPACT
 #define KISSAT_NOPTIONS
 #define KISSAT_NPROOFS
 #define KISSAT_QUIET
 
+#ifdef KISSAT_NDEBUG
 #define KISSAT_assert(ignore) ((void)0)
+#else
+#define KISSAT_assert(cond) assert(cond)
+#endif
 
 #include "misc/util/abc_global.h"
 
diff --git a/src/sat/kissat/kimits.c b/src/sat/kissat/kimits.c
index f5507e0985..f83a4865a1 100644
--- a/src/sat/kissat/kimits.c
+++ b/src/sat/kissat/kimits.c
@@ -99,7 +99,7 @@ static void init_enabled (kissat *solver) {
   } while (0)
 
 void kissat_init_limits (kissat *solver) {
-  KISSAT_assert (solver->statistics.searches == 1);
+  KISSAT_assert (solver->statistics_.searches == 1);
 
   init_enabled (solver);
 
diff --git a/src/sat/kissat/statistics.c b/src/sat/kissat/statistics.c
index 3a3c4bd3c9..e767638cab 100644
--- a/src/sat/kissat/statistics.c
+++ b/src/sat/kissat/statistics.c
@@ -15,6 +15,8 @@
 #include <stdio.h>
 #include <string.h>
 
+ABC_NAMESPACE_IMPL_START
+
 void kissat_print_glue_usage (kissat *solver) {
   const int64_t stable = solver->statistics.clauses_used_stable;
   const int64_t focused = solver->statistics.clauses_used_focused;
@@ -346,8 +348,16 @@ kissat_statistics_print (kissat * solver, bool verbose)
 
 // clang-format on
 
+ABC_NAMESPACE_IMPL_END
+
 #elif defined(KISSAT_NDEBUG)
+
+ABC_NAMESPACE_IMPL_START
+
 int kissat_statistics_dummy_to_avoid_warning;
+
+ABC_NAMESPACE_IMPL_END
+
 #endif
 
 /*------------------------------------------------------------------------*/
@@ -356,6 +366,8 @@ int kissat_statistics_dummy_to_avoid_warning;
 
 #include "inlinevector.h"
 
+ABC_NAMESPACE_IMPL_START
+
 void kissat_check_statistics (kissat *solver) {
   if (solver->inconsistent)
     return;
@@ -402,7 +414,7 @@ void kissat_check_statistics (kissat *solver) {
   KISSAT_assert (!(binary & 1));
   binary /= 2;
 
-  statistics *statistics = &solver->statistics;
+  statistics *statistics = &solver->statistics_;
   KISSAT_assert (statistics->clauses_binary == binary);
   KISSAT_assert (statistics->clauses_redundant == redundant);
   KISSAT_assert (statistics->clauses_irredundant == irredundant);
@@ -413,4 +425,6 @@ void kissat_check_statistics (kissat *solver) {
 #endif
 }
 
+ABC_NAMESPACE_IMPL_END
+
 #endif