diff --git a/tests/unit/unittest/smallstringtest.cpp b/tests/unit/unittest/smallstringtest.cpp
index 19fbc82057cb4caf3a221902a8f5b0fa53048789..cca754b87945c2a3d63c1257a4ffe25258a9ecf1 100644
--- a/tests/unit/unittest/smallstringtest.cpp
+++ b/tests/unit/unittest/smallstringtest.cpp
@@ -291,7 +291,7 @@ TEST(SmallString, BeginPlusOneIsEqualEndForSmallStringWidthSizeOne)
 {
     SmallString text("x");
 
-    auto beginPlusOne = text.begin() + 1l;
+    auto beginPlusOne = text.begin() + std::size_t(1);
 
     ASSERT_THAT(beginPlusOne, Eq(text.end()));
 }