diff --git a/byterun/include/stack.h b/byterun/include/stack.h
index 9ffe4a794..8412790ac 100644
--- a/byterun/include/stack.h
+++ b/byterun/include/stack.h
@@ -328,7 +328,7 @@ static inline void **var_by_category(enum VarCategory category, size_t id) {
       s_failure(&s,
                 "can't read arguments: too big id"); //, %i >= %ul", id, count);
     }
-    return ((void **)d->contents) + count - id; // order is not important
+    return ((void **)d->contents) + id + 1; // order is not important
   }
 
   return var;
diff --git a/byterun/src/interpreter.c b/byterun/src/interpreter.c
index c47c3e4a1..432881936 100644
--- a/byterun/src/interpreter.c
+++ b/byterun/src/interpreter.c
@@ -395,6 +395,7 @@ void run_main(Bytefile* bf, int argc, char **argv) {
           s_failure(&s, "closure");
         }
 #endif
+        s_rotate_n(args_count);
         // NOTE: call_offset < 0 => deal with closure of builtin function
         s_push_i(BOX(call_offset));
 
diff --git a/byterun/src/module_manager.cpp b/byterun/src/module_manager.cpp
index 763c98747..5d992438e 100644
--- a/byterun/src/module_manager.cpp
+++ b/byterun/src/module_manager.cpp
@@ -12,32 +12,33 @@ extern "C" {
 
 #include <filesystem>
 #include <map>
-#include <optional>
 #include <string>
 #include <unordered_map>
 #include <vector>
 
-template <size_t N, typename... Args>
+template <size_t N, bool return_value, typename... Args>
   requires(N == 0)
 void call_func(void (*f)(), size_t n, Args... args) {
-  // std::cout << std::endl << "args_count=" << n << " "; // TODO FIXME TMP
-  std::cout << std::endl; // TODO: TMP, to work with problematic \n display
   asm volatile("movq %0, %%r11"
                : /* no outputs */
                : "m"(n));
-  /*s_push(*/ ((void (*)(Args...))f)(args...); //);
-  s_push(0);
+  if constexpr (return_value) {
+    s_push(((void *(*)(Args...))f)(args...));
+  } else {
+    ((void (*)(Args...))f)(args...);
+    s_push(0);
+  }
 }
 
-template <size_t N, typename... Args>
+template <size_t N, bool return_value, typename... Args>
   requires(N != 0)
 void call_func(void (*f)(), size_t n, Args... args) {
   void *arg = s_pop();
-  call_func<N - 1, Args..., void *>(f, n, arg, args...);
+  call_func<N - 1, return_value, Args..., void *>(f, n, arg, args...);
   // TODO: check that arg is added on the right position
 }
 
-template <size_t N, bool do_check = true>
+template <size_t N, bool return_value, bool do_check = true>
 void call_anyarg_func(void (*f)(), size_t n) {
   if constexpr (do_check) {
     if (n > N) {
@@ -45,9 +46,9 @@ void call_anyarg_func(void (*f)(), size_t n) {
     }
   }
   if (n == N) {
-    call_func<N>(f, n);
+    call_func<N, return_value>(f, n);
   } else if constexpr (N > 0) {
-    call_anyarg_func<N - 1, false>(f, n);
+    call_anyarg_func<N - 1, return_value, false>(f, n);
   }
 }
 
@@ -591,7 +592,7 @@ void run_stdlib_func(BUILTIN id, size_t args_count) {
     break;
   case BUILTIN_Lassert:
     // NOTE: basic params: .args_count = 2, .is_vararg = true
-    call_anyarg_func<20>((void (*)()) & Lassert, args_count);
+    call_anyarg_func<20, false>((void (*)()) & Lassert, args_count);
     break;
   case BUILTIN_Lstring:
     ret = Lstring(s_nth_i(0)); // .is_args = true
@@ -641,7 +642,7 @@ void run_stdlib_func(BUILTIN id, size_t args_count) {
     break;
   case BUILTIN_Lsprintf:
     // NOTE: basic params: .args_count = 1, .is_vararg = true
-    call_anyarg_func<20>((void (*)()) & Lsprintf, args_count);
+    call_anyarg_func<20, true>((void (*)()) & Lsprintf, args_count);
     break;
   case BUILTIN_Lsubstring:
     // std::cout << "substr\n";
@@ -707,7 +708,7 @@ void run_stdlib_func(BUILTIN id, size_t args_count) {
     break;
   case BUILTIN_Lprintf:
     // NOTE: basic params: .args_count = 1, .is_vararg = true
-    call_anyarg_func<20>((void (*)()) & Lprintf, args_count);
+    call_anyarg_func<20, false>((void (*)()) & Lprintf, args_count);
     break;
   case BUILTIN_Lfopen:
     ret = (void *)Lfopen((char *)*s_nth(1), (char *)*s_nth(0));
@@ -736,7 +737,7 @@ void run_stdlib_func(BUILTIN id, size_t args_count) {
     break;
   case BUILTIN_Lfprintf:
     // NOTE: basic params: .args_count = 2, .is_vararg = true
-    call_anyarg_func<20>((void (*)()) & Lfprintf, args_count);
+    call_anyarg_func<20, false>((void (*)()) & Lfprintf, args_count);
     break;
   case BUILTIN_Lregexp:
     ret = (void *)Lregexp((char *)*s_nth(0));
@@ -751,7 +752,7 @@ void run_stdlib_func(BUILTIN id, size_t args_count) {
     break;
   case BUILTIN_Lfailure:
     // NOTE: basic params: .args_count = 1, .is_vararg = true
-    call_anyarg_func<20>((void (*)()) & Lfailure, args_count);
+    call_anyarg_func<20, false>((void (*)()) & Lfailure, args_count);
     break;
   case BUILTIN_Lsystem:
     ret = (void *)Lsystem((char *)*s_nth(0));
diff --git a/byterun/stdlib_regression_check.sh b/byterun/stdlib_regression_check.sh
index da68e1e54..673f5965f 100755
--- a/byterun/stdlib_regression_check.sh
+++ b/byterun/stdlib_regression_check.sh
@@ -31,11 +31,16 @@ for test in ../stdlib/regression/*.lama; do
   # echo "" | ./byterun.exe -p $test_file.bc
   # echo "" | ./byterun.exe -vi $test_file.bc
   echo "" | ./byterun.exe -vi $test_file.bc > test.log
-  # sed '1d;s/^..//' $test_file.t > test_orig.log
-  # diff test.log test_orig.log
+  sed '1d;2d;3d;s/^..//' $test_path.t > test_orig.log
+  # echo "Result:"
+  # cat test.log
+  # echo "Original:"
+  # cat test_orig.log
+  echo "Diff:"
+  diff test.log test_orig.log
 
   rm $test_file.bc
-  # rm test.log test_orig.log
+  rm test.log test_orig.log
   echo "done"
 done