diff --git a/test/src/unit-cbor.cpp b/test/src/unit-cbor.cpp
index a8bbe463..b22f744e 100644
--- a/test/src/unit-cbor.cpp
+++ b/test/src/unit-cbor.cpp
@@ -1271,7 +1271,7 @@ TEST_CASE("CBOR regressions", "[!throws]")
     SECTION("improve code coverage")
     {
         // exotic edge case
-        CHECK_THROWS_AS(json::check_length(0xffffffffffffffff, 0xfffffffffffffff0, 0xff), std::out_of_range);
+        CHECK_THROWS_AS(json::check_length(0xffffffffffffffffull, 0xfffffffffffffff0ull, 0xff), std::out_of_range);
     }
 }
 
diff --git a/test/src/unit-concepts.cpp b/test/src/unit-concepts.cpp
index d65f7401..cdc104b6 100644
--- a/test/src/unit-concepts.cpp
+++ b/test/src/unit-concepts.cpp
@@ -72,8 +72,8 @@ TEST_CASE("concepts")
         // X::size_type must return an unsigned integer
         CHECK((std::is_unsigned<json::size_type>::value));
         // X::size_type can represent any non-negative value of X::difference_type
-        CHECK(std::numeric_limits<json::difference_type>::max() <=
-              std::numeric_limits<json::size_type>::max());
+        CHECK(static_cast<size_t>(std::numeric_limits<json::difference_type>::max()) <=
+              static_cast<size_t>(std::numeric_limits<json::size_type>::max()));
 
         // the expression "X u" has the post-condition "u.empty()"
         {
diff --git a/test/src/unit-msgpack.cpp b/test/src/unit-msgpack.cpp
index 34befb56..cc459fee 100644
--- a/test/src/unit-msgpack.cpp
+++ b/test/src/unit-msgpack.cpp
@@ -389,7 +389,7 @@ TEST_CASE("MessagePack")
                     numbers.push_back(-65536);
                     numbers.push_back(-77777);
                     numbers.push_back(-1048576);
-                    numbers.push_back(-2147483648);
+                    numbers.push_back(-2147483648ll);
                     for (auto i : numbers)
                     {
                         CAPTURE(i);