diff --git a/ops.c b/ops.c
index 74ec73b..8e6cc66 100644
--- a/ops.c
+++ b/ops.c
@@ -239,8 +239,7 @@ OP_DEF(set)
 		r->value.f = a->value.f;
 	} else if (b->type == STRING) {
 		a->type = STRING;
-		if (a->value.p != 0)
-			free((void *)a->value.p);
+		free((void *)a->value.p);
 		a->value.p = (uint32_t)strclone((char *)b->value.p);
 		r->type = STRING;
 		r->value.p = (uint32_t)strclone((char *)a->value.p);
diff --git a/parser.c b/parser.c
index cc09d99..68104f6 100644
--- a/parser.c
+++ b/parser.c
@@ -75,6 +75,8 @@ instance *inewinstance(void)
 void idelline(variable **ops);
 void idelinstance(instance *it)
 {
+	itryfree(it->ret);
+
 	for (uint32_t i = 0; i < MAX_LINES; i++) {
 		if (it->lines[i] == 0)
 			continue;
@@ -93,7 +95,6 @@ void idelinstance(instance *it)
 	free(it->names);
 
 	free(it->stack);
-	itryfree(it->ret);
 	free(it);
 }
 
@@ -230,7 +231,12 @@ loop:
 		// move result global variable "ANS"
 		variable *ret = igetvar(it, "ANS");
 		ret->type = it->ret->type;
-		ret->value.p = it->ret->value.p;
+		if (ret->type == STRING) {
+			free((void *)ret->value.p);
+			ret->value.p = (uint32_t)strclone((char *)it->ret->value.p);
+		} else {
+			ret->value.p = it->ret->value.p;
+		}
 		itryfree(it->ret);
 		it->ret = ret;
 	}
@@ -349,7 +355,7 @@ variable *isolve_(instance *it, variable **ops, uint32_t count)
 					return 0;
 
 				if (!(it->sindent & SKIP)) {
-					variable *v = !ops[aidx]->tmp ? varclone(ops[aidx]) : ops[aidx];
+					variable *v = !ops[aidx]->tmp ? make_varf(0, 0.0f) : ops[aidx];
 					if (func(v, ops[aidx], ops[bidx]) != 0)
 						return 0;
 					ops[aidx] = v;
diff --git a/test6 b/test6
new file mode 100644
index 0000000..bc17de2
--- /dev/null
+++ b/test6
@@ -0,0 +1,10 @@
+# test6
+# used to fix memory leak in setting defined strings
+
+test = "hello"
+test = "fail"
+a = test
+test = "acd"
+
+print(a)
+print(test)