diff --git a/vlib/net/http/header.v b/vlib/net/http/header.v
index dadf13305b..c05bdbc091 100644
--- a/vlib/net/http/header.v
+++ b/vlib/net/http/header.v
@@ -554,21 +554,17 @@ pub fn (h Header) render(flags HeaderRenderConfig) string {
 			} else {
 				data_keys[0]
 			}
-			sb.write_string(key)
-			sb.write_string(': ')
-			for i in 0 .. data_keys.len - 1 {
-				k := data_keys[i]
+			for k in data_keys {
 				for v in h.data[k] {
+					sb.write_string(key)
+					sb.write_string(': ')
 					sb.write_string(v)
-					sb.write_string(',')
+					sb.write_string('\r\n')
 				}
 			}
-			k := data_keys[data_keys.len - 1]
-			sb.write_string(h.data[k].join(','))
-			sb.write_string('\r\n')
 		}
 	} else {
-		for k, v in h.data {
+		for k, vs in h.data {
 			key := if flags.version == .v2_0 {
 				k.to_lower()
 			} else if flags.canonicalize {
@@ -576,10 +572,12 @@ pub fn (h Header) render(flags HeaderRenderConfig) string {
 			} else {
 				k
 			}
-			sb.write_string(key)
-			sb.write_string(': ')
-			sb.write_string(v.join(','))
-			sb.write_string('\r\n')
+			for v in vs {
+				sb.write_string(key)
+				sb.write_string(': ')
+				sb.write_string(v)
+				sb.write_string('\r\n')
+			}
 		}
 	}
 	res := sb.str()
diff --git a/vlib/net/http/header_test.v b/vlib/net/http/header_test.v
index 55eb2bedc3..4f5f2cef64 100644
--- a/vlib/net/http/header_test.v
+++ b/vlib/net/http/header_test.v
@@ -190,15 +190,18 @@ fn test_render_version() ? {
 
 	s1_0 := h.render(version: .v1_0)
 	assert s1_0.contains('accept: foo\r\n')
-	assert s1_0.contains('Accept: bar,baz\r\n')
+	assert s1_0.contains('Accept: bar\r\n')
+	assert s1_0.contains('Accept: baz\r\n')
 
 	s1_1 := h.render(version: .v1_1)
 	assert s1_1.contains('accept: foo\r\n')
-	assert s1_1.contains('Accept: bar,baz\r\n')
+	assert s1_1.contains('Accept: bar\r\n')
+	assert s1_1.contains('Accept: baz\r\n')
 
 	s2_0 := h.render(version: .v2_0)
 	assert s2_0.contains('accept: foo\r\n')
-	assert s2_0.contains('accept: bar,baz\r\n')
+	assert s2_0.contains('accept: bar\r\n')
+	assert s2_0.contains('accept: baz\r\n')
 }
 
 fn test_render_coerce() ? {
@@ -209,15 +212,21 @@ fn test_render_coerce() ? {
 	h.add(.host, 'host')
 
 	s1_0 := h.render(version: .v1_1, coerce: true)
-	assert s1_0.contains('accept: foo,bar,baz\r\n')
+	assert s1_0.contains('accept: foo\r\n')
+	assert s1_0.contains('accept: bar\r\n')
+	assert s1_0.contains('accept: baz\r\n')
 	assert s1_0.contains('Host: host\r\n')
 
 	s1_1 := h.render(version: .v1_1, coerce: true)
-	assert s1_1.contains('accept: foo,bar,baz\r\n')
+	assert s1_1.contains('accept: foo\r\n')
+	assert s1_1.contains('accept: bar\r\n')
+	assert s1_1.contains('accept: baz\r\n')
 	assert s1_1.contains('Host: host\r\n')
 
 	s2_0 := h.render(version: .v2_0, coerce: true)
-	assert s2_0.contains('accept: foo,bar,baz\r\n')
+	assert s2_0.contains('accept: foo\r\n')
+	assert s2_0.contains('accept: bar\r\n')
+	assert s2_0.contains('accept: baz\r\n')
 	assert s2_0.contains('host: host\r\n')
 }
 
@@ -230,17 +239,20 @@ fn test_render_canonicalize() ? {
 
 	s1_0 := h.render(version: .v1_1, canonicalize: true)
 	assert s1_0.contains('Accept: foo\r\n')
-	assert s1_0.contains('Accept: bar,baz\r\n')
+	assert s1_0.contains('Accept: bar\r\n')
+	assert s1_0.contains('Accept: baz\r\n')
 	assert s1_0.contains('Host: host\r\n')
 
 	s1_1 := h.render(version: .v1_1, canonicalize: true)
 	assert s1_1.contains('Accept: foo\r\n')
-	assert s1_1.contains('Accept: bar,baz\r\n')
+	assert s1_1.contains('Accept: bar\r\n')
+	assert s1_1.contains('Accept: baz\r\n')
 	assert s1_1.contains('Host: host\r\n')
 
 	s2_0 := h.render(version: .v2_0, canonicalize: true)
 	assert s2_0.contains('accept: foo\r\n')
-	assert s2_0.contains('accept: bar,baz\r\n')
+	assert s2_0.contains('accept: bar\r\n')
+	assert s2_0.contains('accept: baz\r\n')
 	assert s2_0.contains('host: host\r\n')
 }
 
@@ -252,15 +264,21 @@ fn test_render_coerce_canonicalize() ? {
 	h.add(.host, 'host')
 
 	s1_0 := h.render(version: .v1_1, coerce: true, canonicalize: true)
-	assert s1_0.contains('Accept: foo,bar,baz\r\n')
+	assert s1_0.contains('Accept: foo\r\n')
+	assert s1_0.contains('Accept: bar\r\n')
+	assert s1_0.contains('Accept: baz\r\n')
 	assert s1_0.contains('Host: host\r\n')
 
 	s1_1 := h.render(version: .v1_1, coerce: true, canonicalize: true)
-	assert s1_1.contains('Accept: foo,bar,baz\r\n')
+	assert s1_1.contains('Accept: foo\r\n')
+	assert s1_1.contains('Accept: bar\r\n')
+	assert s1_1.contains('Accept: baz\r\n')
 	assert s1_1.contains('Host: host\r\n')
 
 	s2_0 := h.render(version: .v2_0, coerce: true, canonicalize: true)
-	assert s2_0.contains('accept: foo,bar,baz\r\n')
+	assert s2_0.contains('accept: foo\r\n')
+	assert s2_0.contains('accept: bar\r\n')
+	assert s2_0.contains('accept: baz\r\n')
 	assert s2_0.contains('host: host\r\n')
 }
 
@@ -271,8 +289,8 @@ fn test_str() ? {
 	h.add_custom('X-custom', 'Hello') ?
 
 	// key order is not guaranteed
-	assert h.str() == 'Accept: text/html,image/jpeg\r\nX-custom: Hello\r\n'
-		|| h.str() == 'X-custom: Hello\r\nAccept:text/html,image/jpeg\r\n'
+	assert h.str() == 'Accept: text/html\r\nAccept: image/jpeg\r\nX-custom: Hello\r\n'
+		|| h.str() == 'X-custom: Hello\r\nAccept:text/html\r\nAccept: image/jpeg\r\n'
 }
 
 fn test_header_from_map() ? {
@@ -359,3 +377,11 @@ fn test_parse_headers() ? {
 		return error('should have errored, but got $x')
 	}
 }
+
+fn test_set_cookie() {
+	// multiple Set-Cookie headers should be sent when rendered
+	mut h := new_header()
+	h.add(.set_cookie, 'foo')
+	h.add(.set_cookie, 'bar')
+	assert h.render() == 'Set-Cookie: foo\r\nSet-Cookie: bar\r\n'
+}