diff --git a/workspace_tools/host_tests/echo.py b/workspace_tools/host_tests/echo.py
index e855cb4a1c..75e534fb84 100644
--- a/workspace_tools/host_tests/echo.py
+++ b/workspace_tools/host_tests/echo.py
@@ -37,6 +37,13 @@ class EchoTest():
         selftest.mbed.flush()
         selftest.notify("HOST: Starting the ECHO test")
         result = True
+        
+        """ This ensures that there are no parasites left in the serial buffer.
+        """
+        for i in range(0, 2):
+            selftest.mbed.serial_write("\n")
+            c = selftest.mbed.serial_readline()
+            
         for i in range(0, self.TEST_LOOP_COUNT):
             TEST_STRING = str(uuid.uuid4()) + "\n"
             selftest.mbed.serial_write(TEST_STRING)
diff --git a/workspace_tools/targets.py b/workspace_tools/targets.py
index a633286f7f..da1fce138b 100644
--- a/workspace_tools/targets.py
+++ b/workspace_tools/targets.py
@@ -415,7 +415,7 @@ class K20D50M(Target):
         self.detect_code = ["0230"]
 
 class TEENSY3_1(Target):
-    OUTPUT_EXT = '.hex'
+    OUTPUT_EXT = 'hex'
     
     def __init__(self):
         Target.__init__(self)
@@ -742,7 +742,7 @@ class NRF51822(Target):
             'offset' : 0x14000
         }
     ]
-    OUTPUT_EXT = '.hex'
+    OUTPUT_EXT = 'hex'
     MERGE_SOFT_DEVICE = True
 
     def __init__(self):
diff --git a/workspace_tools/toolchains/__init__.py b/workspace_tools/toolchains/__init__.py
index 09d3f577d1..c780042ac8 100644
--- a/workspace_tools/toolchains/__init__.py
+++ b/workspace_tools/toolchains/__init__.py
@@ -633,6 +633,8 @@ class mbedToolchain:
 
     def link_program(self, r, tmp_path, name):
         ext = 'bin'
+        if hasattr(self.target, 'OUTPUT_EXT'):
+            ext = self.target.OUTPUT_EXT
 
         if hasattr(self.target, 'OUTPUT_NAMING'):
             self.var("binary_naming", self.target.OUTPUT_NAMING)
@@ -641,7 +643,6 @@ class mbedToolchain:
                 ext = ext[0:3]
 
         filename = name+'.'+ext
-
         elf = join(tmp_path, name + '.elf')
         bin = join(tmp_path, filename)
 
@@ -657,9 +658,6 @@ class mbedToolchain:
         self.var("compile_succeded", True)
         self.var("binary", filename)
 
-        if hasattr(self.target, 'OUTPUT_EXT'):
-            bin = bin.replace('.bin', self.target.OUTPUT_EXT)
-
         return bin
 
     def default_cmd(self, command):