diff --git a/index.js b/index.js
index 6f2d0f8..62e2681 100644
--- a/index.js
+++ b/index.js
@@ -34,7 +34,7 @@ var map = {
   pb: Math.pow(1024, 5),
 };
 
-var parseRegExp = /^((-|\+)?(\d+(?:\.\d+)?)) *(kb|mb|gb|tb|pb)$/i;
+var parseRegExp = /^((-|\+)?(\d+(?:\.\d+)?)) *(b|kb|mb|gb|tb|pb)$/i;
 
 /**
  * Convert the given value in bytes into a string or parse to string to an integer in bytes.
diff --git a/test/byte-parse.js b/test/byte-parse.js
index cebfab2..13fc091 100644
--- a/test/byte-parse.js
+++ b/test/byte-parse.js
@@ -103,6 +103,9 @@ describe('Test byte parse function', function(){
   it('Should drop partial bytes', function(){
     assert.equal(bytes.parse('1.1b'), 1);
     assert.equal(bytes.parse('1.0001kb'), 1024);
+    // the `b` unit must floor like every other unit (not truncate toward zero)
+    assert.equal(bytes.parse('-1.9b'), -2);
+    assert.equal(bytes.parse('-1.9kb'), Math.floor(-1.9 * 1024));
   });
 
   it('Should allow whitespace', function(){