diff --git a/cmd/tools/vcover/cover_test.v b/cmd/tools/vcover/cover_test.v
index 26ec600db0..e4d5299ff3 100644
--- a/cmd/tools/vcover/cover_test.v
+++ b/cmd/tools/vcover/cover_test.v
@@ -34,6 +34,10 @@ fn np(path string) string {
 }
 
 fn test_simple() {
+	// if true {
+	// return
+	//}
+
 	t1 := np(os.join_path(tfolder, 't1'))
 	t2 := np(os.join_path(tfolder, 't2'))
 	t3 := np(os.join_path(tfolder, 't3'))
diff --git a/vlib/builtin/map.v b/vlib/builtin/map.v
index 382bec968e..2ea56e3eea 100644
--- a/vlib/builtin/map.v
+++ b/vlib/builtin/map.v
@@ -259,6 +259,7 @@ fn map_free_string(pkey voidptr) {
 fn map_free_nop(_ voidptr) {
 }
 
+@[markused]
 fn new_map(key_bytes int, value_bytes int, hash_fn MapHashFn, key_eq_fn MapEqFn, clone_fn MapCloneFn, free_fn MapFreeFn) map {
 	metasize := int(sizeof(u32) * (init_capicity + extra_metas_inc))
 	// for now assume anything bigger than a pointer is a string
diff --git a/vlib/v/ast/table.v b/vlib/v/ast/table.v
index f9258c6998..f6caee8429 100644
--- a/vlib/v/ast/table.v
+++ b/vlib/v/ast/table.v
@@ -32,6 +32,7 @@ pub mut:
 	used_veb_types   []Type          // veb context types, filled in by checker
 	used_maps        int             // how many times maps were used, filled in by markused
 	used_arrays      int             // how many times arrays were used, filled in by markused
+	// json             bool            // json is imported
 }
 
 @[unsafe]
@@ -65,7 +66,7 @@ pub mut:
 	sumtypes           map[int]SumTypeDecl
 	cmod_prefix        string // needed for ast.type_to_str(Type) while vfmt; contains `os.`
 	is_fmt             bool
-	used_features      &UsedFeatures = &UsedFeatures{} // filled in by the checker/markused, when pref.skip_unused = true;
+	used_features      &UsedFeatures = &UsedFeatures{} // filled in by the builder via markused module, when pref.skip_unused = true;
 	veb_res_idx_cache  int // Cache of `veb.Result` type
 	veb_ctx_idx_cache  int // Cache of `veb.Context` type
 	panic_handler      FnPanicHandler = default_table_panic_handler
diff --git a/vlib/v/markused/markused.v b/vlib/v/markused/markused.v
index a8d0caa12c..fd630cd43b 100644
--- a/vlib/v/markused/markused.v
+++ b/vlib/v/markused/markused.v
@@ -196,6 +196,9 @@ pub fn mark_used(mut table ast.Table, mut pref_ pref.Preferences, ast_files []&a
 			all_fn_root_names << k
 			continue
 		}
+		// if mfn.name == 'before_request' {
+		// all_fn_root_names << k
+		//}
 
 		// sync:
 		if k == 'sync.new_channel_st' {
@@ -338,6 +341,8 @@ pub fn mark_used(mut table ast.Table, mut pref_ pref.Preferences, ast_files []&a
 
 	if 'C.cJSON_Parse' in all_fns {
 		all_fn_root_names << 'tos5'
+		all_fn_root_names << 'time.unix' // used by json
+		table.used_features.used_maps++ // json needs new_map etc
 	}
 	mut walker := Walker.new(
 		table:       table
@@ -349,6 +354,7 @@ pub fn mark_used(mut table ast.Table, mut pref_ pref.Preferences, ast_files []&a
 	)
 	// println( all_fns.keys() )
 	walker.mark_markused_fns() // tagged with `@[markused]`
+
 	walker.mark_markused_consts() // tagged with `@[markused]`
 	walker.mark_markused_globals() // tagged with `@[markused]`
 	walker.mark_exported_fns()
@@ -405,6 +411,7 @@ pub fn mark_used(mut table ast.Table, mut pref_ pref.Preferences, ast_files []&a
 			walker.mark_const_as_used(kcon)
 		}
 	}
+
 	table.used_features.used_fns = walker.used_fns.move()
 	table.used_features.used_consts = walker.used_consts.move()
 	table.used_features.used_globals = walker.used_globals.move()
diff --git a/vlib/v/pref/pref.v b/vlib/v/pref/pref.v
index 749843bdef..bc757b2487 100644
--- a/vlib/v/pref/pref.v
+++ b/vlib/v/pref/pref.v
@@ -335,6 +335,7 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 		res.use_cache = true
 		res.skip_unused = true
 	} */
+	mut no_skip_unused := false
 
 	mut command, mut command_idx := '', 0
 	for i := 0; i < args.len; i++ {
@@ -602,6 +603,7 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 				res.skip_unused = true
 			}
 			'-no-skip-unused' {
+				no_skip_unused = true
 				res.skip_unused = false
 			}
 			'-compress' {
@@ -1134,6 +1136,13 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 	res.build_options = m.keys()
 	// eprintln('>> res.build_options: $res.build_options')
 	res.fill_with_defaults()
+	if res.backend == .c {
+		// res.skip_unused = true
+		if no_skip_unused {
+			res.skip_unused = false
+		}
+	}
+
 	return res, command
 }