diff --git a/src/MySQL_Connection.cpp b/src/MySQL_Connection.cpp
index 7cbf83a..d50312b 100644
--- a/src/MySQL_Connection.cpp
+++ b/src/MySQL_Connection.cpp
@@ -58,8 +58,8 @@ const char DISCONNECTED[] PROGMEM = "Disconnected.";
 
   Returns boolean - True = connection succeeded
 */
-boolean MySQL_Connection::connect(IPAddress server, int port, char *user,
-                                  char *password, char *db)
+boolean MySQL_Connection::connect(IPAddress server, int port, const char *user,
+                                  const char *password, const char *db)
 {
   int connected = 0;
   int retries = MAX_CONNECT_ATTEMPTS;
diff --git a/src/MySQL_Connection.h b/src/MySQL_Connection.h
index 6537b99..1816996 100644
--- a/src/MySQL_Connection.h
+++ b/src/MySQL_Connection.h
@@ -42,8 +42,8 @@ class MySQL_Connection : public MySQL_Packet {
   public:
     MySQL_Connection(Client *client_instance) :
         MySQL_Packet(client_instance) {}
-    boolean connect(IPAddress server, int port, char *user, char *password,
-                    char *db=NULL);
+    boolean connect(IPAddress server, int port, const char *user, const char *password,
+                    const char *db=NULL);
     int connected() { return client->connected(); }
     const char *version() { return MYSQL_VERSION_STR; }
     void close();
diff --git a/src/MySQL_Packet.cpp b/src/MySQL_Packet.cpp
index b9c0cf7..0820f3d 100644
--- a/src/MySQL_Packet.cpp
+++ b/src/MySQL_Packet.cpp
@@ -94,8 +94,8 @@ void MySQL_Packet::show_error(const char *msg, bool EOL) {
   password[in]    password
   db[in]          default database
 */
-void MySQL_Packet::send_authentication_packet(char *user, char *password,
-                                              char *db)
+void MySQL_Packet::send_authentication_packet(const char *user, const char *password,
+                                              const char *db)
 {
   if (buffer != NULL)
     free(buffer);
@@ -175,7 +175,7 @@ void MySQL_Packet::send_authentication_packet(char *user, char *password,
 
   Returns boolean - True = scramble succeeded
 */
-boolean MySQL_Packet::scramble_password(char *password, byte *pwd_hash) {
+boolean MySQL_Packet::scramble_password(const char *password, byte *pwd_hash) {
   byte *digest;
   byte hash1[20];
   byte hash2[20];
diff --git a/src/MySQL_Packet.h b/src/MySQL_Packet.h
index 20399f1..135aa80 100644
--- a/src/MySQL_Packet.h
+++ b/src/MySQL_Packet.h
@@ -63,10 +63,10 @@ class MySQL_Packet {
 
     MySQL_Packet(Client *client_instance);
     boolean complete_handshake(char *user, char *password);
-    void send_authentication_packet(char *user, char *password,
-                                    char *db=NULL);
+    void send_authentication_packet(const char *user, const char *password,
+                                    const char *db=NULL);
     void parse_handshake_packet();
-    boolean scramble_password(char *password, byte *pwd_hash);
+    boolean scramble_password(const char *password, byte *pwd_hash);
     void read_packet();
     int get_packet_type();
     void parse_error_packet();