diff --git a/tests/src/unit-allocator.cpp b/tests/src/unit-allocator.cpp
index ea9386fcb..8fa9034b5 100644
--- a/tests/src/unit-allocator.cpp
+++ b/tests/src/unit-allocator.cpp
@@ -1167,6 +1167,10 @@ TEST_CASE("parse() survives a failing allocation at every point (#5985)")
     // terminates the program instead of throwing std::bad_alloc. Nothing to
     // check there.
 #if !(defined(_ITERATOR_DEBUG_LEVEL) && _ITERATOR_DEBUG_LEVEL > 0)
+    // Clang 3.4 and 3.5 leak memory when an element constructor throws
+    // inside libstdc++'s containers (a std::map copy, a std::vector
+    // reallocation), without any json value involved.
+#if !(defined(__clang__) && !defined(__apple_build_version__) && __clang_major__ == 3 && __clang_minor__ < 6)
     SECTION("parser callback")
     {
         const auto keep_all = [](int /*depth*/, sweep_json::parse_event_t /*event*/, sweep_json& /*parsed*/) noexcept
@@ -1201,5 +1205,6 @@ TEST_CASE("parse() survives a failing allocation at every point (#5985)")
         });
     }
 #endif
+#endif
 }
 #endif
diff --git a/tests/src/unit-custom-object-key-type.cpp b/tests/src/unit-custom-object-key-type.cpp
index acb78d628..9149bbfb6 100644
--- a/tests/src/unit-custom-object-key-type.cpp
+++ b/tests/src/unit-custom-object-key-type.cpp
@@ -160,12 +160,12 @@ class strict_key
     }
 
   private:
-    std::string m_value{};
+    std::string m_value;
 };
 
 strict_key make_strict_key(const std::string& key)
 {
-    return strict_key(key.c_str());
+    return {key.c_str()};
 }
 
 template<class Key, class Value, class Compare, class Allocator>
@@ -224,7 +224,9 @@ TEST_CASE("converting a value with keys that cannot be made from a std::string n
         }
     }
 
-    const strict_json converted = value;
+    // direct-initialization: a copy-initialization makes GCC 4.8 instantiate the
+    // copy constructor, which needs a range constructor strict_object lacks
+    const strict_json converted(value);
 
     // at() needs to make a std::string of a key for its error message
     const auto member = [](const strict_json & object, const char* name) -> const strict_json &
diff --git a/tests/src/unit-stream-bulk-scan.cpp b/tests/src/unit-stream-bulk-scan.cpp
index 0e0fbd72e..90cf702e3 100644
--- a/tests/src/unit-stream-bulk-scan.cpp
+++ b/tests/src/unit-stream-bulk-scan.cpp
@@ -120,6 +120,20 @@ class oversized_get_area_streambuf : public std::streambuf
   private:
     std::array<char, 8> m_data{{'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'}};
 };
+
+// the size the oversized_get_area_streambuf claims: 3 GiB with a 64-bit
+// std::size_t, else 0 to skip the test (tag dispatch, as a constant condition
+// triggers MSVC's C4127)
+template<std::size_t SizeOfSizeT>
+std::size_t oversized_get_area_size(std::integral_constant<std::size_t, SizeOfSizeT> /*unused*/)
+{
+    return 0;
+}
+
+std::size_t oversized_get_area_size(std::integral_constant<std::size_t, 8> /*unused*/)
+{
+    return std::size_t{3} << 30u;
+}
 #endif
 
 // how a test reads from the stream
@@ -466,7 +480,7 @@ TEST_CASE("parsing from a std::istream scans the get area in bulk")
     SECTION("skipping more characters than gbump() takes at once")
     {
         // gbump() takes an int, but a get area can be larger
-        const std::size_t claimed = sizeof(std::size_t) < 8 ? 0 : std::size_t{3} << 30u;
+        const std::size_t claimed = oversized_get_area_size(std::integral_constant<std::size_t, sizeof(std::size_t)>());
         oversized_get_area_streambuf buf(claimed);
         if (claimed == 0 || static_cast<std::size_t>(buf.in_avail()) != claimed)
         {