diff --git a/src/json.hpp b/src/json.hpp
old mode 100644
new mode 100755
index 9511f02cc..319f541cb
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -2931,8 +2931,8 @@ class basic_json
     */
     template <class InteratorType, typename
               std::enable_if<
-                  std::is_same<InteratorType, typename basic_json::iterator>::value or
-                  std::is_same<InteratorType, typename basic_json::const_iterator>::value
+                  std::is_same<InteratorType, typename __basic_json::iterator>::value or
+                  std::is_same<InteratorType, typename __basic_json::const_iterator>::value
                   , int>::type
               = 0>
     InteratorType erase(InteratorType first, InteratorType last)
@@ -4286,7 +4286,9 @@ class basic_json
 
         // We only reach this line if we cannot compare values. In that case,
         // we compare types.
-        return lhs_type < rhs_type;
+        // Have to use operator< explicitly in order to
+        // not cause ambiguity on MS compiler
+        return operator<(lhs_type, rhs_type);
     }
 
     /*!
@@ -4852,7 +4854,7 @@ class basic_json
     };
 
     /// an iterator value
-    union internal_iterator
+    struct internal_iterator
     {
         /// iterator for JSON objects
         typename object_t::iterator object_iterator;
diff --git a/test/unit.cpp b/test/unit.cpp
old mode 100644
new mode 100755
index e38305190..f1863fb7b
--- a/test/unit.cpp
+++ b/test/unit.cpp
@@ -6939,7 +6939,7 @@ TEST_CASE("lexicographical comparison operators")
                     CAPTURE(i);
                     CAPTURE(j);
                     // check precomputed values
-                    CHECK( (j_types[i] < j_types[j]) == expected[i][j] );
+                    CHECK(operator<(j_types[i], j_types[j]) == expected[i][j]);
                 }
             }
         }
@@ -8163,9 +8163,11 @@ TEST_CASE("parser class")
             SECTION("escaped")
             {
                 // quotation mark "\""
-                CHECK(json::parser("\"\\\"\"").parse() == R"("\"")"_json);
+                auto r1 = R"("\"")"_json;
+                CHECK(json::parser("\"\\\"\"").parse() == r1);
                 // reverse solidus "\\"
-                CHECK(json::parser("\"\\\\\"").parse() == R"("\\")"_json);
+                auto r2 = R"("\\")"_json;
+                CHECK(json::parser("\"\\\\\"").parse() == r2);
                 // solidus
                 CHECK(json::parser("\"\\/\"").parse() == R"("/")"_json);
                 // backspace
@@ -9738,7 +9740,8 @@ TEST_CASE("regression tests")
         {
             auto s = "[\"\\\"foo\\\"\"]";
             json j = json::parse(s);
-            CHECK(j == R"(["\"foo\""])"_json);
+            auto expected = R"(["\"foo\""])"_json;
+            CHECK(j == expected);
         }
     }