diff --git a/README.md b/README.md
index da91f85..8b05586 100644
--- a/README.md
+++ b/README.md
@@ -127,7 +127,7 @@ number := decimal | hex | octal | binary
 
 decimal := integer ('.' [0-9]+)? exponent?
 exponent := ('e' | 'E') integer
-integer := sign? [1-9] [0-9_]*
+integer := sign? [0-9] [0-9_]*
 sign := '+' | '-'
 
 hex := '0x' [0-9a-fA-F] [0-9a-fA-F_]*
diff --git a/src/parser.rs b/src/parser.rs
index 280b149..66c1fea 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -297,6 +297,7 @@ mod tests {
 
     #[test]
     fn test_integer() {
+        assert_eq!(integer("0"), Ok(("", 0)));
         assert_eq!(integer("0123456789"), Ok(("", 123456789)));
         assert_eq!(integer("0123_456_789"), Ok(("", 123456789)));
         assert_eq!(integer("0123_456_789_"), Ok(("", 123456789)));