diff --git a/vlib/builtin/builtin.v b/vlib/builtin/builtin.v
index 919c86e35e..8bc049bcf8 100644
--- a/vlib/builtin/builtin.v
+++ b/vlib/builtin/builtin.v
@@ -105,7 +105,7 @@ __global nr_mallocs int = 0
 
 [unsafe_fn]
 pub fn malloc(n int) byteptr {
-	if n < 0 {
+	if n <= 0 {
 		panic('malloc(<0)')
 	}
 	$if prealloc {
diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index 17886c8411..d235d12afe 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -1126,6 +1126,9 @@ pub fn (s []string) join_lines() string {
 
 // reverse will return a new reversed string.
 pub fn (s string) reverse() string {
+	if s.len == 0 {
+		return ''
+	}
 	mut res := string {
 		len: s.len
 		str: malloc(s.len)
diff --git a/vlib/encoding/base64/base64.v b/vlib/encoding/base64/base64.v
index f708f267d9..08208b3a1e 100644
--- a/vlib/encoding/base64/base64.v
+++ b/vlib/encoding/base64/base64.v
@@ -24,7 +24,11 @@ const (
  * NB: if you need to decode many strings repeatedly, take a look at decode_in_buffer too.
  */
 pub fn decode(data string) string {
-	buffer := malloc( data.len * 3 / 4 )
+	size := data.len * 3 / 4
+	if size <= 0 {
+		return ''
+	}
+	buffer := malloc(size)
 	return tos(buffer, decode_in_buffer(data, buffer) )
 }
 
@@ -36,7 +40,11 @@ pub fn decode(data string) string {
  * NB: if you need to encode many strings repeatedly, take a look at encode_in_buffer too.
  */
 pub fn encode(data string) string {
-	buffer := malloc( 4 * ((data.len + 2) / 3) )
+	size := 4 * ((data.len + 2) / 3)
+	if size <= 0 {
+		return ''
+	}
+	buffer := malloc(size)
 	return tos(buffer, encode_in_buffer(data, buffer))
 }