diff --git a/libraries/ArduinoTestSuite/examples/ATS_SD_File/ATS_SD_File.pde b/libraries/ArduinoTestSuite/examples/ATS_SD_File/ATS_SD_File.pde
index 95527fefd..c4894200f 100644
--- a/libraries/ArduinoTestSuite/examples/ATS_SD_File/ATS_SD_File.pde
+++ b/libraries/ArduinoTestSuite/examples/ATS_SD_File/ATS_SD_File.pde
@@ -15,11 +15,25 @@ void setup()
   ATS_PrintTestStatus("SD.begin()", b = SD.begin(4));
   if (!b) goto done;
   
-  f = SD.open("test.txt", true, false);
+  f = SD.open("test.txt", SD_TRUNCATE);
   ATS_PrintTestStatus("SD.open()", f);
   if (!f) goto done;
   
-  f.print("abcdefgh");
+  f.print("1234");
+  f.close();
+  
+  f = SD.open("test.txt", SD_TRUNCATE);
+  ATS_PrintTestStatus("SD.open()", f);
+  if (!f) goto done;
+  
+  f.print("abcde");
+  f.close();
+  
+  f = SD.open("test.txt", SD_APPEND);
+  ATS_PrintTestStatus("SD.open()", f);
+  if (!f) goto done;
+  
+  f.print("fgh");
   f.close();
   
   f = SD.open("test.txt");
@@ -57,7 +71,7 @@ void setup()
   
   f.close();  
 
-  f = SD.open("test2.txt", true, false);
+  f = SD.open("test2.txt", SD_TRUNCATE);
   ATS_PrintTestStatus("SD.open()", f);
   if (!f) goto done;
   
diff --git a/libraries/ArduinoTestSuite/examples/ATS_SD_Files/ATS_SD_Files.pde b/libraries/ArduinoTestSuite/examples/ATS_SD_Files/ATS_SD_Files.pde
index 50a7a741d..9bd842a8e 100644
--- a/libraries/ArduinoTestSuite/examples/ATS_SD_Files/ATS_SD_Files.pde
+++ b/libraries/ArduinoTestSuite/examples/ATS_SD_Files/ATS_SD_Files.pde
@@ -13,7 +13,7 @@ void setup()
   if (!b) goto done;
   
   ATS_PrintTestStatus("!SD.exists()", !SD.exists("asdf.txt"));
-  ATS_PrintTestStatus("SD.open()", f = SD.open("asdf.txt", true)); f.close();
+  ATS_PrintTestStatus("SD.open()", f = SD.open("asdf.txt", SD_TRUNCATE)); f.close();
   ATS_PrintTestStatus("SD.exists()", SD.exists("asdf.txt"));
   ATS_PrintTestStatus("SD.exists()", SD.exists("/asdf.txt"));
   ATS_PrintTestStatus("SD.remove()", SD.remove("asdf.txt"));
@@ -48,13 +48,13 @@ void setup()
   ATS_PrintTestStatus("!SD.exists()", !SD.exists("x/y"));  
   ATS_PrintTestStatus("!SD.exists()", !SD.exists("x/y/z"));  
   
-  ATS_PrintTestStatus("!SD.open()", !(f = SD.open("asdf/asdf.txt", true))); f.close();
+  ATS_PrintTestStatus("!SD.open()", !(f = SD.open("asdf/asdf.txt", SD_TRUNCATE))); f.close();
   ATS_PrintTestStatus("!SD.exists()", !SD.exists("asdf"));
   ATS_PrintTestStatus("!SD.exists()", !SD.exists("asdf.txt"));
   ATS_PrintTestStatus("!SD.exists()", !SD.exists("asdf/asdf.txt"));
   ATS_PrintTestStatus("SD.mkdir()", SD.mkdir("asdf"));
   ATS_PrintTestStatus("SD.exists()", SD.exists("asdf"));
-  ATS_PrintTestStatus("SD.open()", f = SD.open("asdf/asdf.txt", true)); f.close();
+  ATS_PrintTestStatus("SD.open()", f = SD.open("asdf/asdf.txt", SD_TRUNCATE)); f.close();
   ATS_PrintTestStatus("SD.exists()", SD.exists("asdf/asdf.txt"));
   ATS_PrintTestStatus("!SD.rmdir()", !SD.rmdir("asdf"));
   ATS_PrintTestStatus("SD.exists()", SD.exists("asdf"));
diff --git a/libraries/SD/SD.cpp b/libraries/SD/SD.cpp
index 2faade5aa..356a2986a 100644
--- a/libraries/SD/SD.cpp
+++ b/libraries/SD/SD.cpp
@@ -343,7 +343,7 @@ boolean SDClass::begin(uint8_t csPin) {
 }
 
 
-File SDClass::open(char *filepath, boolean write, boolean append) {
+File SDClass::open(char *filepath, uint8_t mode) {
   /*
 
      Open the supplied file path for reading or writing.
@@ -369,18 +369,7 @@ File SDClass::open(char *filepath, boolean write, boolean append) {
 
   // TODO: Allow for read&write? (Possibly not, as it requires seek.)
 
-  uint8_t oflag = O_RDONLY;
-
-  if (write) {
-    oflag = O_CREAT | O_WRITE;
-    if (append) {
-      oflag |= O_APPEND;
-    } else {
-      oflag |= O_TRUNC;
-    }
-  }
-  
-  fileOpenMode = oflag;
+  fileOpenMode = mode;
   walkPath(filepath, root, callback_openPath, this);
 
   return File();
diff --git a/libraries/SD/SD.h b/libraries/SD/SD.h
index 774e3d968..6d81ee5c8 100644
--- a/libraries/SD/SD.h
+++ b/libraries/SD/SD.h
@@ -20,6 +20,10 @@
 #include <utility/SdFat.h>
 #include <utility/SdFatUtil.h>
 
+#define SD_READ O_READ
+#define SD_TRUNCATE (O_WRITE | O_CREAT | O_TRUNC)
+#define SD_APPEND (O_WRITE | O_CREAT | O_APPEND)
+
 class File : public Stream {
 public:
   virtual void write(uint8_t);
@@ -49,7 +53,7 @@ public:
   // Open the specified file/directory with the supplied mode (e.g. read or
   // write, etc). Returns a File object for interacting with the file.
   // Note that currently only one file can be open at a time.
-  File open(char *filename, boolean write = false, boolean append = true);
+  File open(char *filename, uint8_t mode = SD_READ);
 
   // Methods to determine if the requested file path exists.
   boolean exists(char *filepath);