diff --git a/libraries/mbed/common/retarget.cpp b/libraries/mbed/common/retarget.cpp
index 14720f785e..2a481d17e0 100644
--- a/libraries/mbed/common/retarget.cpp
+++ b/libraries/mbed/common/retarget.cpp
@@ -122,7 +122,7 @@ static inline int openmode_to_posix(int openmode) {
     if (openmode & _LLIO_APPEND) posix |= O_APPEND;
     if (openmode & _LLIO_TRUNC ) posix |= O_TRUNC;
 #endif
-    return posix;
+    return posix & ~O_BINARY;
 }
 
 extern "C" FILEHANDLE PREFIX(_open)(const char* name, int openmode) {