diff --git a/libr/esil/esil.c b/libr/esil/esil.c
index 0e59f79a99..c82de1473a 100644
--- a/libr/esil/esil.c
+++ b/libr/esil/esil.c
@@ -18,7 +18,7 @@
 #define IFDBG if (esil && esil->verbose > 1)
 
 static inline void free_ornot(void *p) {
-	R_CONST_FREE (p);
+	R_TAG_FREE (p);
 }
 
 /* Returns the number that has bits + 1 least significant bits set. */
@@ -54,7 +54,7 @@ static bool r_esil_runpending(REsil *esil, char *pending) {
 	} else if (esil->pending) {
 		char *expr = esil->pending;
 		esil->pending = NULL;
-		r_esil_parse (esil, R_CONST_UNTAG (expr));
+		r_esil_parse (esil, R_TAG_NOP (expr));
 		free_ornot (expr);
 		return true;
 	}
diff --git a/libr/include/r_types_base.h b/libr/include/r_types_base.h
index 82134b013a..fb2dd5018f 100644
--- a/libr/include/r_types_base.h
+++ b/libr/include/r_types_base.h
@@ -263,11 +263,24 @@ typedef struct _utX {
 #define R_IS_DIRTY(x) (x)->is_dirty
 #define R_DIRTY_VAR bool is_dirty
 
-#define R_CONST_MAYBE
-#define R_CONST_TAG(x) ((x)|1)
-#define R_CONST_UNTAG(x) (void*)((((size_t)x)>>1)<<1)
-#define R_CONST_FREE(x) do { if (!((size_t)(x)&1)) { R_FREE(x); }} while(0)
-#define R_IS_CONST(x) ((size_t)(x)&1))
+#define R_TAG(x) (void*)((size_t)(x)|1)
+#define R_UNTAG(x) (void*)((((size_t)(x))&(size_t)-2))
+#define R_TAG_FREE(x) do { if (!((size_t)(x)&1)) { R_FREE(x); }} while(0)
+#define R_TAG_NOP(x) untagged_pointer_check(x)
+#define R_IS_TAGGED(x) ((size_t)(x)&1)
+#define R_TAGGED
+#if R_CHECKS_LEVEL == 0
+static inline void *untagged_pointer_check(void *x) {
+	return x;
+}
+#else
+static inline void *untagged_pointer_check(void *x) {
+	if (R_IS_TAGGED(x)) {
+		int *p = (int*)0; *p = 0;
+	}
+	return x;
+}
+#endif
 
 #ifdef __cplusplus
 }
diff --git a/test/unit/test_util.c b/test/unit/test_util.c
index d5325398f7..83bdaa1b4e 100644
--- a/test/unit/test_util.c
+++ b/test/unit/test_util.c
@@ -151,11 +151,34 @@ bool test_file_slurp(void) {
 	mu_end;
 }
 
+R_ALIGNED(4) static const char msg[] = "Hello World"; // const strings can have the lowerbit set
+R_TAGGED void *tagged(bool owned) {
+	if (owned) {
+		void *res = strdup ("hello world");
+		return R_TAG_NOP (res);
+	}
+	return R_TAG (msg);
+}
+
+bool test_tagged_pointers(void) {
+	void *a = tagged (false);
+	void *b = tagged (true);
+	// eprintf ("%p %p\n", a, b);
+	// eprintf ("%d %d\n", (size_t)a&1, (size_t)b&1);
+	mu_assert_eq (R_IS_TAGGED (a), 1, "tagged");
+	char *msg = R_UNTAG (a);
+	mu_assert_streq (msg, "Hello World", "faileq");
+	mu_assert_eq (R_IS_TAGGED (b), 0, "not tagged");
+	char *msg2 = R_UNTAG (b);
+	mu_assert_streq (msg2, "hello world", "faileq");
+	R_TAG_FREE (a);
+	R_TAG_FREE (b);
+	mu_end;
+}
+
 bool test_initial_underscore(void) {
 	Sdb *TDB = setup_sdb ();
-	char *s;
-
-	s = r_type_func_guess (TDB, "sym._strchr");
+	char *s = r_type_func_guess (TDB, "sym._strchr");
 	mu_assert_notnull (s, "sym._ should be ignored");
 	mu_assert_streq (s, "strchr", "strchr should be identified");
 	free (s);
@@ -212,6 +235,7 @@ int all_tests() {
 	mu_run_test (test_autonames);
 	mu_run_test (test_file_slurp);
 	mu_run_test (test_initial_underscore);
+	mu_run_test (test_tagged_pointers);
 	return tests_passed != tests_run;
 }