diff --git a/include/tinycsocket.h b/include/tinycsocket.h
index a6fe3f4..228075e 100644
--- a/include/tinycsocket.h
+++ b/include/tinycsocket.h
@@ -229,7 +229,7 @@ struct TcsAddress
     TcsAddressFamily family;
     union
     {
-        char _storage[24]; /**< Ensures full zero-initialization when copied from TCS_ADDRESS_NONE */
+        unsigned char _storage[24]; /**< Ensures full zero-initialization when copied from TCS_ADDRESS_NONE */
         struct
         {
             uint32_t address; /**< Same byte order as the host */
diff --git a/src/tinycsocket_internal.h b/src/tinycsocket_internal.h
index d618279..50cc582 100644
--- a/src/tinycsocket_internal.h
+++ b/src/tinycsocket_internal.h
@@ -223,7 +223,7 @@ struct TcsAddress
     TcsAddressFamily family;
     union
     {
-        char _storage[24]; /**< Ensures full zero-initialization when copied from TCS_ADDRESS_NONE */
+        unsigned char _storage[24]; /**< Ensures full zero-initialization when copied from TCS_ADDRESS_NONE */
         struct
         {
             uint32_t address; /**< Same byte order as the host */