Index: generic/nsfError.c
===================================================================
diff -u -r880487204ff2da18d2d25ebd727b9b4bbda86c8e -r836e08bf2af69a30dcd2cf6bb2e19f97d798b98a
--- generic/nsfError.c	(.../nsfError.c)	(revision 880487204ff2da18d2d25ebd727b9b4bbda86c8e)
+++ generic/nsfError.c	(.../nsfError.c)	(revision 836e08bf2af69a30dcd2cf6bb2e19f97d798b98a)
@@ -68,9 +68,13 @@
    * buffer (rather than the number of required bytes as required by C99) and
    * upon other error conditions. This should not happen for the above size
    * estimation, however. Also, for MS VC runtimes, we use the vendor-specific
-   * _vscprintf() 
+   * _vscprintf()
+   *
+   * Note: For MinGW and MinGW-w64, we assume that their ANSI-compliant
+   * version of vsnprintf() is used. See __USE_MINGW_ANSI_STDIO in nsfInt.h
    */
-#if defined(_WIN32) && defined(_MSC_VER)
+
+#if defined(_MSC_VER)
   failure = (result == -1 && errno == ERANGE);
 #else
   assert(result > -1);
@@ -79,7 +83,7 @@
 
   if (failure) {
     int addedStringLength;
-#if defined(_WIN32) && defined(_MSC_VER)   
+#if defined(_MSC_VER)   
     /* Compute the required size of the Tcl_DString */
     va_copy(vargsCopy, vargs);
     addedStringLength = _vscprintf(fmt, vargsCopy);
Index: generic/nsfInt.h
===================================================================
diff -u -r880487204ff2da18d2d25ebd727b9b4bbda86c8e -r836e08bf2af69a30dcd2cf6bb2e19f97d798b98a
--- generic/nsfInt.h	(.../nsfInt.h)	(revision 880487204ff2da18d2d25ebd727b9b4bbda86c8e)
+++ generic/nsfInt.h	(.../nsfInt.h)	(revision 836e08bf2af69a30dcd2cf6bb2e19f97d798b98a)
@@ -35,6 +35,21 @@
 # define HAVE_UINTPTR_T 
 #endif
 
+/*
+ * MinGW and MinGW-w64 provide both MSCRT-compliant and ANSI-compliant
+ * implementations of certain I/O operations (e.g., *printf()). By
+ * setting __USE_MINGW_ANSI_STDIO to 1 explicitly, we can assume the
+ * ANSI versions.
+ *
+ * Note: It is sufficient to test for __MINGW32__ to trap all MinGW
+ * tool chains, including 64bit versions. See
+ * http://sourceforge.net/p/predef/wiki/Compilers/#mingw-and-mingw-w64
+ */
+
+#if defined(__MINGW32__) && !defined(__USE_MINGW_ANSI_STDIO)
+#define __USE_MINGW_ANSI_STDIO 1
+#endif
+
 #include <tclInt.h>
 #include "nsf.h"
 
@@ -1057,7 +1072,6 @@
 #endif
 #endif
 
-
 #if !defined(NDEBUG)
 /*# define NSF_INLINE*/
 #endif