diff --git a/src/lib/lexer.mll b/src/lib/lexer.mll
index 954abb364..6e007fb55 100644
--- a/src/lib/lexer.mll
+++ b/src/lib/lexer.mll
@@ -171,11 +171,10 @@ let tyvar_start = '\''
 (* Ensure an operator cannot start with comment openings *)
 let oper_char = ['!''%''&''*''+''-''.''/'':''<''=''>''@''^''|']
 let oper_char_no_slash = ['!''%''&''*''+''-''.'':''<''=''>''@''^''|']
+let oper_char_no_star = ['!''%''&''+''-''.''/'':''<''=''>''@''^''|']
 let oper_char_no_slash_star = ['!''%''&''+''-''.'':''<''=''>''@''^''|']
-let operator1 = oper_char
-let operator2 = oper_char oper_char_no_slash_star | oper_char_no_slash oper_char
-let operatorn = oper_char oper_char_no_slash_star (oper_char* ('_' ident)?) | oper_char_no_slash oper_char (oper_char* ('_' ident)?) | oper_char ('_' ident)?
-let operator = operator1 | operator2 | operatorn
+
+let operator = ((oper_char_no_slash_star* ['/']? oper_char_no_slash_star*) | oper_char_no_slash*) ('_' ident)?
 let escape_sequence = ('\\' ['\\''\"''\'''n''t''b''r']) | ('\\' digit digit digit) | ('\\' 'x' hexdigit hexdigit)
 let lchar = [^'\n']
 
@@ -188,7 +187,7 @@ rule token comments = parse
       token comments lexbuf }
   | "@"                                 { At }
   | "2" ws "^"                          { TwoCaret }
-  | "^"					{ Caret }
+  | "^"                                 { Caret }
   | "::"                                { ColonColon }
   | ":"                                 { Colon ":" }
   | ","                                 { Comma }
diff --git a/test/format/default/operator.expect b/test/format/default/operator.expect
new file mode 100644
index 000000000..ae87f009a
--- /dev/null
+++ b/test/format/default/operator.expect
@@ -0,0 +1,96 @@
+default Order dec
+$include <prelude.sail>
+
+// comment
+//comment
+/// line_comment with more than two slash
+///line_comment with more than two slash
+//// line_comment with more than two slash
+////line_comment with more than two slash
+// /*/*/
+/*/ block_comment with slash near  and
+*/
+//* line_block_comment */
+infix 4 ===_u
+infix 4 ===/_u
+
+infix 4 ===*_u
+val operator ===/_u : forall 'n. (int('n), int('n)) -> bool
+function operator ===/_u(x, y) = x == y
+
+infix 4 =/
+val operator =/ : forall 'n. (int('n), int('n)) -> bool
+function operator =/(x, y) = x == y
+
+infix 4 =
+
+// comment
+infix 4 </>
+
+// comment
+infix 4 =/
+
+// comment
+infix 4 ==/
+infix 4 -/-
+
+//comment
+infix 4 /--
+
+//comment
+infixl 4 =
+
+// comment
+infixl 4 =/
+
+// comment
+infixl 4 ==/
+infixl 4 -/-
+
+//comment
+infixl 4 -/-
+
+//comment
+infixl 4 /--
+
+//comment
+infixr 4 =
+
+// comment
+infixr 4 =/
+
+// comment
+infixr 4 ==/
+infixr 4 -/-
+
+//comment
+infixr 4 -/-
+
+//comment
+infixr 4 /--
+
+//comment
+function f () = {
+    if op_eq2_with_block_comment == /**/ /**/ 1 then { 1 };
+
+    if op_eq_slash =/ 1 then { 1 };
+    if op_eq_slash_with_block_comment =/ 1 then /**/ { 1 };
+
+    let op_eq_with_line_comment =
+        //
+        1;
+
+    let op_eq_with_line_comment =
+        ///
+        1;
+
+    if op_eq_with_line_comment =
+        // comment
+        if eq_slash = /**/ 1 then { 1 } else { 2 } then { 1 };
+
+    if eq_with_blcok_comment = /**/ 1 then { 1 };
+
+    if eq3_slash ===/_u 1 then { 1 };
+
+    0
+}
diff --git a/test/format/operator.sail b/test/format/operator.sail
new file mode 100644
index 000000000..e8b527aa7
--- /dev/null
+++ b/test/format/operator.sail
@@ -0,0 +1,72 @@
+default Order dec
+$include <prelude.sail>
+
+// comment
+//comment
+/// line_comment with more than two slash
+///line_comment with more than two slash
+//// line_comment with more than two slash
+////line_comment with more than two slash
+
+// /*/*/
+
+/*/ block_comment with slash near /* and */ 
+*/
+
+
+//* line_block_comment */
+
+infix 4 ===_u
+infix 4 ===/_u
+
+infix 4 ===*_u
+val operator ===/_u : forall 'n. (int('n), int('n)) -> bool
+function operator ===/_u(x, y) = x == y
+
+infix 4 =/
+val operator =/ : forall 'n. (int('n), int('n)) -> bool
+function operator =/(x, y) = x == y
+
+infix 4 = // comment
+infix 4 </> // comment
+infix 4 =/ // comment
+infix 4 ==/
+infix 4 -/- //comment
+infix 4 /-- //comment
+
+infixl 4 = // comment
+infixl 4 =/ // comment
+infixl 4 ==/
+infixl 4 -/- //comment
+infixl 4 -/- //comment
+infixl 4 /-- //comment
+
+infixr 4 = // comment
+infixr 4 =/ // comment
+infixr 4 ==/
+infixr 4 -/- //comment
+infixr 4 -/- //comment
+infixr 4 /-- //comment
+
+function f () = {
+    if op_eq2_with_block_comment /**/== /**/ 1 then { 1 };
+    
+    if op_eq_slash =/1 then { 1 };
+    if op_eq_slash_with_block_comment =/1/**/ then { 1 };
+
+    let op_eq_with_line_comment = //
+    1;
+
+    let op_eq_with_line_comment = ///
+    1;
+
+    if op_eq_with_line_comment = // comment
+    (if eq_slash = /**/1 then { 1 } else {2}) then {1};
+
+    if eq_with_blcok_comment = /**/1 then { 1 };
+
+
+    if eq3_slash ===/_u 1 then { 1 };
+    
+    0
+}