diff --git a/Adafruit_GPS.cpp b/Adafruit_GPS.cpp
index 65b8b1e..8732074 100644
--- a/Adafruit_GPS.cpp
+++ b/Adafruit_GPS.cpp
@@ -247,7 +247,7 @@ void Adafruit_GPS::begin(uint16_t baud)
   delay(10);
 }
 
-void Adafruit_GPS::sendCommand(char *str) {
+void Adafruit_GPS::sendCommand(const char *str) {
   if(gpsSwSerial) gpsSwSerial->println(str);
   else            gpsHwSerial->println(str);
 }
diff --git a/Adafruit_GPS.h b/Adafruit_GPS.h
index 273097d..7c7dd38 100644
--- a/Adafruit_GPS.h
+++ b/Adafruit_GPS.h
@@ -94,7 +94,9 @@ class Adafruit_GPS {
   char *lastNMEA(void);
   boolean newNMEAreceived();
   void common_init(void);
-  void sendCommand(char *);
+
+  void sendCommand(const char *);
+  
   void pause(boolean b);
 
   boolean parseNMEA(char *response);