diff --git a/vlib/builtin/array_test.v b/vlib/builtin/array_test.v
index 1795d7d289..2bb37eac6f 100644
--- a/vlib/builtin/array_test.v
+++ b/vlib/builtin/array_test.v
@@ -22,7 +22,7 @@ fn test_pointer() {
 }
 
 fn test_assign() {
-	arr := [2, 4, 8, 16, 32, 64, 128]
+	mut arr := [2, 4, 8, 16, 32, 64, 128]
 
 	arr[0] = 2
 	arr[1] &= 255
@@ -99,7 +99,7 @@ struct K {
 }
 
 fn test_empty() {
-	mut chunks := []Chunk
+	mut chunks := []Chunk{}
 	a := Chunk{}
 	assert chunks.len == 0
 	chunks << a
@@ -111,7 +111,7 @@ fn test_empty() {
 }
 
 fn test_push() {
-	mut a := []int
+	mut a := []int{}
 	a << 1
 	a << 3
 	assert a[1] == 3
@@ -289,7 +289,7 @@ fn test_reverse() {
 	for i, _ in d {
 		assert d[i] == b[b.len - i - 1]
 	}
-	e := []int
+	e := []int{}
 	f := e.reverse()
 	assert f.len == 0
 }
@@ -711,7 +711,7 @@ fn test_hex(){
 }
 
 fn test_left_shift_precendence() {
-	mut arr := []int
+	mut arr := []int{}
 	arr << 1 + 1
 	arr << 1 - 1
 	arr << 2 / 1
diff --git a/vlib/crypto/rand/rand.v b/vlib/crypto/rand/rand.v
index c7f02c874b..c3bc04aa27 100644
--- a/vlib/crypto/rand/rand.v
+++ b/vlib/crypto/rand/rand.v
@@ -11,7 +11,7 @@ const (
 // NOTE: temp until we have []bytes(buff)
 fn c_array_to_bytes_tmp(len int, buffer voidptr) []byte {
 
-	mut arr := []byte
+	mut arr := []byte{}
 	arr = make(len, 1, 1)
 	arr.data = buffer
 	/*
diff --git a/vlib/crypto/rand/rand_test.v b/vlib/crypto/rand/rand_test.v
index 0d76c5a6b4..41e2b199f5 100644
--- a/vlib/crypto/rand/rand_test.v
+++ b/vlib/crypto/rand/rand_test.v
@@ -31,7 +31,7 @@ fn test_crypto_rand_read() {
 
 fn test_crypto_rand_int_u64() {
 	max := u64(160)
-	mut unique := []int
+	mut unique := []int{}
 	for _ in 0..80 {
 		r := rand.int_u64(max) or {
 			assert false
diff --git a/vlib/crypto/rand/utils.v b/vlib/crypto/rand/utils.v
index 27091115b2..14cfdb84c2 100644
--- a/vlib/crypto/rand/utils.v
+++ b/vlib/crypto/rand/utils.v
@@ -4,10 +4,8 @@
 
 module rand
 
-import(
-	math.bits
-	encoding.binary
-)
+import math.bits
+import encoding.binary
 
 pub fn int_u64(max u64) ?u64 {
 	bitlen := bits.len_64(max)
diff --git a/vlib/rand/rand.v b/vlib/rand/rand.v
index d7126510f9..9ccd681b40 100644
--- a/vlib/rand/rand.v
+++ b/vlib/rand/rand.v
@@ -16,7 +16,7 @@ pub fn next(max int) int {
 
 // rand_r returns a pseudo-random number;
 // writes a result value to the seed argument.
-pub fn rand_r(seed mut int) int {
+pub fn rand_r(seed &int) int {
 	ns := *seed * 1103515245 + 12345
 	(*seed) = ns
 	return ns & 0x7fffffff
diff --git a/vlib/v/tests/map_to_string_test.v b/vlib/v/tests/map_to_string_test.v
index 7af0b3a80a..4bb27921a4 100644
--- a/vlib/v/tests/map_to_string_test.v
+++ b/vlib/v/tests/map_to_string_test.v
@@ -5,21 +5,26 @@ struct Test {
 }
 
 fn test_interpolation_map_to_string() {
-	a := map[string]string
+	if true {
+
+	}
+	//
+	else{}
+	mut a := map[string]string
 	a['1'] = 'one'
 	a['2'] = 'two'
 	a['3'] = 'three'
 	assert '$a' == 'map_string_string{1: one, 2: two, 3: three}'
-	b := map[string]int
+	mut b := map[string]int
 	b['1'] = 1
 	b['2'] = 2
 	b['3'] = 3
 	assert '$b' == 'map_string_int{1: 1, 2: 2, 3: 3}'
-	c := map[string]bool
+	mut c := map[string]bool
 	c['1'] = true
 	c['2'] = false
 	assert '$c' == 'map_string_bool{1: true, 2: false}'
-	d := map[string]Test
+	mut d := map[string]Test
 	d['1'] = Test{true, 0, 'abc'}
 	d['2'] = Test{true, 1, 'def'}
 	d['3'] = Test{false, 2, 'ghi'}
diff --git a/vlib/v/tests/nested_map_test.v b/vlib/v/tests/nested_map_test.v
index 9a4574be7e..92f3a1f282 100644
--- a/vlib/v/tests/nested_map_test.v
+++ b/vlib/v/tests/nested_map_test.v
@@ -1,5 +1,8 @@
 fn test_nested_maps() {
-	x := map[string]map[string]int
+	if true{}
+	//
+	else{}
+	mut x := map[string]map[string]int
 	x["a"] = map[string]int
 	assert x["a"]["b"] == 0
 	x["a"]["b"] = 5