diff --git a/compiler/parser.v b/compiler/parser.v
index c5e686ffb6..bc62eb2cbc 100644
--- a/compiler/parser.v
+++ b/compiler/parser.v
@@ -592,6 +592,9 @@ fn (p mut Parser) struct_decl() {
 		if field_name in names {
 			p.error('duplicate field `$field_name`')
 		}
+		if p.mod != 'os' && contains_capital(field_name) {
+			p.error('struct fields cannot contain uppercase letters, use snake_case instead')
+		} 
 		names << field_name
 		// We are in an interface?
 		// `run() string` => run is a method, not a struct field
diff --git a/vlib/builtin/int_test.v b/vlib/builtin/int_test.v
new file mode 100644
index 0000000000..138871618b
--- /dev/null
+++ b/vlib/builtin/int_test.v
@@ -0,0 +1,7 @@
+const (
+	a = 3
+) 
+
+fn test_const() {
+	assert a == 3 
+}