diff --git a/src/pugixpath.cpp b/src/pugixpath.cpp
index 5071fa0..d94fb34 100644
--- a/src/pugixpath.cpp
+++ b/src/pugixpath.cpp
@@ -1208,7 +1208,7 @@ namespace pugi
 
 		// tree node structure
 		xpath_ast_node* m_left;
-		xpath_ast_node*	m_right;
+		xpath_ast_node* m_right;
 		xpath_ast_node* m_third;
 		xpath_ast_node* m_next;
 
@@ -1857,7 +1857,8 @@ namespace pugi
 			else m_contents = 0;
 		}
 	public:
-		xpath_ast_node(ast_type_t type, const char* contents, xpath_allocator& a): m_type(type), m_rettype(ast_type_none), m_contents(0)
+		xpath_ast_node(ast_type_t type, const char* contents, xpath_allocator& a): m_type(type),
+			m_rettype(ast_type_none), m_left(0), m_right(0), m_third(0), m_next(0), m_contents(0)
 		{
 			set_contents(contents, a);
 		}
diff --git a/tests/test_xpath_functions.cpp b/tests/test_xpath_functions.cpp
index d492da9..9cada22 100644
--- a/tests/test_xpath_functions.cpp
+++ b/tests/test_xpath_functions.cpp
@@ -47,6 +47,7 @@ TEST_XML(xpath_number_sum, "<node>123<child>789</child></node><node/>")
 	CHECK_XPATH_NUMBER(n, "sum(.)", 123789); // 123 .. 789
 	
 	CHECK_XPATH_NUMBER(n, "sum(./descendant-or-self::node())", 125490); // node + 123 + child + 789 = 123789 + 123 + 789 + 789 = 125490
+	CHECK_XPATH_NUMBER(n, "sum(.//node())", 1701); // 123 + child + 789 = 123 + 789 + 789
 	CHECK_XPATH_NUMBER_NAN(doc.last_child(), "sum(.)");
 
 	// sum with 2 arguments
@@ -217,4 +218,27 @@ TEST_XML(xpath_boolean_lang, "<node xml:lang='en'><child xml:lang='ru-UK'><subch
 	CHECK_XPATH_FAIL("lang(1, 2)");
 }
 
+TEST(xpath_string_concat)
+{
+	xml_node c;
+
+	// concat with 0 arguments
+	CHECK_XPATH_FAIL("concat()");
+
+	// concat with 1 argument
+	CHECK_XPATH_FAIL("concat('')");
+
+	// concat with exactly 2 arguments
+	CHECK_XPATH_STRING(c, "concat('prev','next')", "prevnext");
+	CHECK_XPATH_STRING(c, "concat('','next')", "next");
+	CHECK_XPATH_STRING(c, "concat('prev','')", "prev");
+
+	// concat with 3 or more arguments
+	CHECK_XPATH_STRING(c, "concat('a', 'b', 'c')", "abc");
+	CHECK_XPATH_STRING(c, "concat('a', 'b', 'c', 'd')", "abcd");
+	CHECK_XPATH_STRING(c, "concat('a', 'b', 'c', 'd', 'e')", "abcde");
+	CHECK_XPATH_STRING(c, "concat('a', 'b', 'c', 'd', 'e', 'f')", "abcdef");
+	CHECK_XPATH_STRING(c, "concat('a', 'b', 'c', 'd', 'e', 'f', 'g')", "abcdefg");
+}
+
 // $$$: string value of <node>123<child>789</child>100</node> should be 123789100 (?)