diff --git a/src/core.js b/src/core.js
index d8ed38c5..f19de96d 100644
--- a/src/core.js
+++ b/src/core.js
@@ -17,7 +17,7 @@ var jQuery = function( selector, context ) {
 
 	// A simple way to check for HTML strings or ID strings
 	// (both of which we optimize for)
-	quickExpr = /^(?:[^<]*(<[\w\W]+>)[^>]*$|#([\w\-]+)$)/,
+	quickExpr = /^(?:[^<]*(<[\w\W]+>)[^>]*$|#([\w\-]*)$)/,
 
 	// Check if a string has a non-whitespace character in it
 	rnotwhite = /\S/,
diff --git a/test/unit/core.js b/test/unit/core.js
index 6ee8724d..a8da85fc 100644
--- a/test/unit/core.js
+++ b/test/unit/core.js
@@ -12,7 +12,7 @@ test("Basic requirements", function() {
 });
 
 test("jQuery()", function() {
-	expect(24);
+	expect(25);
 
 	// Basic constructor's behavior
 
@@ -20,6 +20,7 @@ test("jQuery()", function() {
 	equals( jQuery(undefined).length, 0, "jQuery(undefined) === jQuery([])" );
 	equals( jQuery(null).length, 0, "jQuery(null) === jQuery([])" );
 	equals( jQuery("").length, 0, "jQuery('') === jQuery([])" );
+	equals( jQuery("#").length, 0, "jQuery('#') === jQuery([])" );
 
 	var obj = jQuery("div");
 	equals( jQuery(obj).selector, "div", "jQuery(jQueryObj) == jQueryObj" );