diff --git a/grammar.g4 b/grammar.g4
index f0aeb44..c1e7826 100644
--- a/grammar.g4
+++ b/grammar.g4
@@ -201,10 +201,10 @@ OPERATOR_TAIL1 : [+\-*/%^!?|&,<>=]+\. ;
 OPERATOR_TAIL2 : [+\-*/%^!?|&,<>=]+\.\. ;
 OPERATOR_TAIL3 : [+\-*/%^!?|&,<>=]+\.\.\. ;
 
-FLOAT_NUMBER_LITERAL : [0-9]+ '.' [0-9]+ 'f' ;
-DOUBLE_NUMBER_LITERAL : [0-9]+ '.' [0-9]+ ;
-INT_LITERAL : [0-9]+ 'i' ;
-LONG_LITERAL : [0-9]+ 'l' ;
+FLOAT_NUMBER_LITERAL : '-'? [0-9]+ '.' [0-9]+ 'f' ;
+DOUBLE_NUMBER_LITERAL : '-'? [0-9]+ '.' [0-9]+ ;
+INT_LITERAL : '-'? [0-9]+ 'i' ;
+LONG_LITERAL : '-'? [0-9]+ 'l' ;
 INDEX_LITERAL : [0-9]+ ;
 STRING_LITERAL : '\"' ([^\\\'] | ( '\\' [\u0000-\u00FF]))* '\"' ;
 UNICODE_STRING_LITERAL : '\"' ([^\\\'] | ( '\\' [\u0000-\uFFFF]))* '\"u';
diff --git a/grammar.js b/grammar.js
index a6c084a..60b0bdf 100644
--- a/grammar.js
+++ b/grammar.js
@@ -306,8 +306,8 @@ module.exports = grammar({
     operator_tail2: $ => /[+\-*/%^!?|&,<>=]+\.\./,
     operator_tail3: $ => /[+\-*/%^!?|&,<>=]+\.\.\./,
 
-    float_literal: $ => /[0-9]+\.[0-9]+f/,
-    double_literal: $ => /[0-9]+\.[0-9]+/,
+    float_literal: $ => /\-?[0-9]+\.[0-9]+f/,
+    double_literal: $ => /\-?[0-9]+\.[0-9]+/,
     int_literal: $ => /\-?[0-9]+i/,
     long_literal: $ => /\-?[0-9]+l/,
     index_literal: $ => /[0-9]+/,