diff --git a/protobuf-parse/src/pure/model.rs b/protobuf-parse/src/pure/model.rs
index 8e2cb5fa9..25a57de47 100644
--- a/protobuf-parse/src/pure/model.rs
+++ b/protobuf-parse/src/pure/model.rs
@@ -426,11 +426,11 @@ impl fmt::Display for ProtobufConstant {
 impl ProtobufConstantMessage {
     pub fn format(&self) -> String {
         let mut s = String::new();
-        write!(s, "{{").unwrap();
+        write!(s, "{{ ").unwrap();
         for (n, v) in &self.fields {
             match v {
                 ProtobufConstant::Message(m) => write!(s, "{} {}", n, m.format()).unwrap(),
-                v => write!(s, "{}: {}", n, v.format()).unwrap(),
+                v => write!(s, "{}: {} ", n, v.format()).unwrap(),
             }
         }
         write!(s, "}}").unwrap();
diff --git a/protobuf-parse/src/pure/parser.rs b/protobuf-parse/src/pure/parser.rs
index a4f16e87a..a61a110b1 100644
--- a/protobuf-parse/src/pure/parser.rs
+++ b/protobuf-parse/src/pure/parser.rs
@@ -377,6 +377,18 @@ impl<'a> Parser<'a> {
         while !self.tokenizer.lookahead_is_symbol('}')? {
             let n = self.next_message_constant_field_name()?;
             let v = self.next_field_value()?;
+
+            // Consume the comma or semicolon if present. Commas and semicolons
+            // between message fields are optional, all these are valid:
+            //
+            //    {foo: 1,bar: 2,baz: 3,}
+            //    {foo: 1;bar: 2;baz: 3;}
+            //    {foo: 1 bar: 2 baz: 3}
+            //    {foo: 1,bar: 2;baz: 3}
+            //    {foo: 1,bar: 2 baz: 3}
+            //
+            self.tokenizer.next_symbol_if_in(&[',', ';'])?;
+
             r.fields.insert(n, v);
         }
         self.tokenizer
@@ -1336,6 +1348,29 @@ mod test {
         assert_eq!("10", mess.t.options[0].value.format());
     }
 
+    #[test]
+    fn test_field_options() {
+        let msg = r#" (my_opt).my_field = {foo: 1 bar: 2} "#;
+        let opt = parse(msg, |p| p.next_field_option());
+        assert_eq!(r#"{ foo: 1 bar: 2 }"#, opt.value.format());
+
+        let msg = r#" (my_opt).my_field = {foo: 1; bar:2;} "#;
+        let opt = parse(msg, |p| p.next_field_option());
+        assert_eq!(r#"{ foo: 1 bar: 2 }"#, opt.value.format());
+
+        let msg = r#" (my_opt).my_field = {foo: 1, bar: 2} "#;
+        let opt = parse(msg, |p| p.next_field_option());
+        assert_eq!(r#"{ foo: 1 bar: 2 }"#, opt.value.format());
+
+        let msg = r#" (my_opt).my_field = "foo" "#;
+        let opt = parse(msg, |p| p.next_field_option());
+        assert_eq!(r#""foo""#, opt.value.format());
+
+        let msg = r#" (my_opt) = { my_field: "foo"} "#;
+        let opt = parse(msg, |p| p.next_field_option());
+        assert_eq!(r#"{ my_field: "foo" }"#, opt.value.format());
+    }
+
     #[test]
     fn test_message() {
         let msg = r#"message ReferenceData
diff --git a/protobuf-support/src/lexer/tokenizer.rs b/protobuf-support/src/lexer/tokenizer.rs
index c5e84a0a9..5541b1d2d 100644
--- a/protobuf-support/src/lexer/tokenizer.rs
+++ b/protobuf-support/src/lexer/tokenizer.rs
@@ -194,11 +194,16 @@ impl<'a> Tokenizer<'a> {
         Ok(())
     }
 
-    pub fn next_symbol_if_eq(&mut self, symbol: char) -> TokenizerResult<bool> {
-        Ok(self.next_token_if(|token| match token {
-            &Token::Symbol(c) if c == symbol => true,
+    pub fn next_symbol_if_in(&mut self, symbols: &[char]) -> TokenizerResult<bool> {
+        self.next_token_if(|token| match token {
+            Token::Symbol(c) if symbols.contains(c) => true,
             _ => false,
-        })? != None)
+        })
+        .map(|token| token.is_some())
+    }
+
+    pub fn next_symbol_if_eq(&mut self, symbol: char) -> TokenizerResult<bool> {
+        self.next_symbol_if_in(&[symbol])
     }
 
     pub fn next_symbol_expect_eq(