diff --git a/doc/grammars/const-expr.peg b/doc/grammars/const-expr.peg
index f5b0a0a..cd98456 100644
--- a/doc/grammars/const-expr.peg
+++ b/doc/grammars/const-expr.peg
@@ -9,15 +9,15 @@ ConstantExpr
   / ConstantFetch
 
 ConstantFloat
-  = [0-9]+ '.' [0-9]* ConstantFloatExp?
-  / [0-9]* '.' [0-9]+ ConstantFloatExp?
-  / [0-9]+ ConstantFloatExp
+  = '-'? [0-9]+ '.' [0-9]* ConstantFloatExp?
+  / '-'? [0-9]* '.' [0-9]+ ConstantFloatExp?
+  / '-'? [0-9]+ ConstantFloatExp
 
 ConstantFloatExp
-  = [eE] [0-9]+
+  = [eE] '-'? [0-9]+
 
 ConstantInt
-  = [0-9]+
+  = '-'? [0-9]+
 
 ConstantTrue
   = [tT][rR][uU][eE]
diff --git a/src/Lexer/Lexer.php b/src/Lexer/Lexer.php
index 701a049..8ba3ef6 100644
--- a/src/Lexer/Lexer.php
+++ b/src/Lexer/Lexer.php
@@ -131,8 +131,8 @@ class Lexer
 			self::TOKEN_CLOSE_PHPDOC => '\\*/',
 			self::TOKEN_PHPDOC_TAG => '@[a-z-]++',
 
-			self::TOKEN_FLOAT => '(?:[0-9]++\\.[0-9]*+(?:e[0-9]++)?)|(?:[0-9]*+\\.[0-9]++(?:e[0-9]++)?)|(?:[0-9]++e[0-9]++)',
-			self::TOKEN_INTEGER => '[0-9]++',
+			self::TOKEN_FLOAT => '(?:-?[0-9]++\\.[0-9]*+(?:e-?[0-9]++)?)|(?:-?[0-9]*+\\.[0-9]++(?:e-?[0-9]++)?)|(?:-?[0-9]++e-?[0-9]++)',
+			self::TOKEN_INTEGER => '-?[0-9]++',
 			self::TOKEN_SINGLE_QUOTED_STRING => '\'(?:\\\\.|[^\'])*+\'',
 			self::TOKEN_DOUBLE_QUOTED_STRING => '"(?:\\\\.|[^"])*+"',