diff --git a/tests/assert.hpp b/tests/assert.hpp
index e6ede15..552d4b7 100644
--- a/tests/assert.hpp
+++ b/tests/assert.hpp
@@ -2,7 +2,8 @@
 #define TESTS_ASSERT_HPP
 
 #include <cstdlib>
+#include <iostream>
 
-#define ASSERT(e) ((void)((e) ? ((void)0) : ((void)fprintf(stderr, "Assertion failed: (%s), function %s, file %s, line %u.\n", #e, __func__, __FILE__, __LINE__), abort())))
+#define ASSERT(e) ((void)((e) ? ((void)0) : ((void)(std::cerr << "Assertion failed: (" << #e << "), function " << __func__ << ", file " << __FILE__ << ", line " << __LINE__ << ".\n"), std::abort())))
 
 #endif /* TESTS_ASSERT_HPP */