diff --git a/Adafruit_GPS.cpp b/Adafruit_GPS.cpp
index 3bca0de..7b5ac95 100755
--- a/Adafruit_GPS.cpp
+++ b/Adafruit_GPS.cpp
@@ -382,9 +382,11 @@ uint8_t Adafruit_GPS::parseHex(char c) {
        return 0;
     if (c <= 'F')
        return (c - 'A')+10;
+    // if (c > 'F')
+    return 0;
 }
 
-boolean Adafruit_GPS::waitForSentence(char *wait4me, uint8_t max) {
+boolean Adafruit_GPS::waitForSentence(const char *wait4me, uint8_t max) {
   char str[20];
 
   uint8_t i=0;
diff --git a/Adafruit_GPS.h b/Adafruit_GPS.h
index a417255..5d513ad 100755
--- a/Adafruit_GPS.h
+++ b/Adafruit_GPS.h
@@ -140,7 +140,7 @@ class Adafruit_GPS {
   boolean fix;
   uint8_t fixquality, satellites;
 
-  boolean waitForSentence(char *wait, uint8_t max = MAXWAITSENTENCE);
+  boolean waitForSentence(const char *wait, uint8_t max = MAXWAITSENTENCE);
   boolean LOCUS_StartLogger(void);
   boolean LOCUS_StopLogger(void);
   boolean LOCUS_ReadStatus(void);