diff --git a/src/format.rs b/src/format.rs
index 3f843b5..88fc419 100644
--- a/src/format.rs
+++ b/src/format.rs
@@ -112,7 +112,7 @@ impl<W: Write> PrettyPrinter<W> {
 }
 
 #[cfg(test)]
-mod test {
+mod test_scss {
     use super::StyleSheet;
     macro_rules! test {
         ($func:ident, $input:literal) => {
@@ -145,6 +145,7 @@ mod test {
 
     test!(empty, "");
     test!(basic_nesting, "a {\n  b {\n  }\n}\n");
+    test!(mul_nesting, "a, b {\n  a, b {\n  }\n}\n");
     test!(ident_with_num, "el1 {\n}\n");
 
     test!(selector_element, "a {\n}\n");
diff --git a/src/lexer.rs b/src/lexer.rs
index 5e7788d..c5aa2d2 100644
--- a/src/lexer.rs
+++ b/src/lexer.rs
@@ -102,7 +102,7 @@ impl<'a> Lexer<'a> {
     fn lex_at_rule(&mut self) -> TokenKind {
         let mut string = String::with_capacity(99);
         while let Some(c) = self.buf.peek() {
-            if !c.is_alphabetic() && c != &'-' {
+            if !c.is_alphabetic() && c != &'-' && c != &'_' {
                 break;
             }
             let tok = self
@@ -163,7 +163,7 @@ impl<'a> Lexer<'a> {
     fn lex_attr(&mut self) -> TokenKind {
         let mut attr = String::with_capacity(99);
         while let Some(c) = self.buf.peek() {
-            if !c.is_alphabetic() && c != &'-' {
+            if !c.is_alphabetic() && c != &'-' && c != &'_' {
                 break;
             }
             let tok = self
@@ -229,7 +229,7 @@ impl<'a> Lexer<'a> {
         let mut case_sensitive = true;
 
         while let Some(c) = self.buf.peek() {
-            if !c.is_alphabetic() && c != &'-' {
+            if !c.is_alphabetic() && c != &'-' && c != &'_' {
                 break;
             }
 
@@ -288,7 +288,7 @@ impl<'a> Lexer<'a> {
         self.pos.next_char();
         let mut name = String::with_capacity(99);
         while let Some(c) = self.buf.peek() {
-            if !c.is_alphabetic() && c != &'-' {
+            if !c.is_alphabetic() && c != &'-' && c != &'_' {
                 break;
             }
             let tok = self
@@ -305,7 +305,7 @@ impl<'a> Lexer<'a> {
         let mut string = String::with_capacity(99);
         while let Some(c) = self.buf.peek() {
             // we know that the first char is alphabetic from peeking
-            if !c.is_alphanumeric() && c != &'-' {
+            if !c.is_alphanumeric() && c != &'-' && c != &'_' {
                 break;
             }
             let tok = self