diff --git a/src/Adafruit_GPS.cpp b/src/Adafruit_GPS.cpp
index bed5c38..fd8086c 100644
--- a/src/Adafruit_GPS.cpp
+++ b/src/Adafruit_GPS.cpp
@@ -352,7 +352,7 @@ char Adafruit_GPS::read(void) {
   // Serial.print(c);
 
   currentline[lineidx] = c;
-  lineidx++;
+  lineidx = lineidx + 1;
   if (lineidx >= MAXLINELENGTH)
     lineidx = MAXLINELENGTH -
               1; // ensure there is someplace to put the next received character
diff --git a/src/NMEA_build.cpp b/src/NMEA_build.cpp
index 832a0c6..e113e53 100644
--- a/src/NMEA_build.cpp
+++ b/src/NMEA_build.cpp
@@ -565,7 +565,13 @@ char *Adafruit_GPS::build(char *nmea, const char *thisSource,
 
   addChecksum(nmea); // Successful completion
   if (!noCRLF) { // Add Carriage Return and Line Feed to comply with NMEA-183
-    sprintf(nmea, "%s\r\n", nmea);
+    int neededSize = strlen(nmea) + 2;
+    char *tempBuffer = (char *)malloc(neededSize);
+    if (tempBuffer != NULL) {
+      sprintf(tempBuffer, neededSize, "%s\r\n", nmea);
+      strcpy(nmea, tempBuffer);
+      free(tempBuffer);
+    }
   }
   return nmea; // return pointer to finished product
 }