diff --git a/include/mtl/string.hpp b/include/mtl/string.hpp
index f627048..3284cb0 100644
--- a/include/mtl/string.hpp
+++ b/include/mtl/string.hpp
@@ -172,8 +172,15 @@ public:
 			num_char = mtl_itostr(x, str.data());
 		}
 #else
-		itoa(x, str.data(), hex ? 16 : 10);
-		num_char = strlen(str.data());
+		if (hex) {
+			if (x > 0) {
+				num_char = snprintf(str.data(), str.capacity() + 1, "%#x", x);
+			} else {
+				num_char = snprintf(str.data(), str.capacity() + 1, "-%#x", -x);
+			}
+		} else {
+			num_char = snprintf(str.data(), str.capacity() + 1, "%i", x);
+		}
 #endif
 		str.m_size = num_char;
 		return str;
@@ -198,8 +205,11 @@ public:
 			num_char = mtl_utostr(x, str.data());
 		}
 #else
-		utoa(x, str.data(), hex ? 16 : 10);
-		num_char = strlen(str.data());
+		if (hex) {
+			num_char = snprintf(str.data(), str.capacity() + 1, "%#x", x);
+		} else {
+			num_char = snprintf(str.data(), str.capacity() + 1, "%u", x);
+		}
 #endif
 		str.m_size = num_char;
 		return str;
@@ -243,8 +253,7 @@ public:
 #ifdef __ARM_ARCH_4T__
 		num_char = mtl_utostrx(reinterpret_cast<uint32_t>(x), str.data());
 #else
-		utoa(x, str.data(), 16);
-		num_char = strlen(str.data());
+		num_char = snprintf(str.data(), str.capacity() + 1, "%#x", x);
 #endif
 		str.m_size = num_char;
 		return str;