diff --git a/libquadmath/ChangeLog b/libquadmath/ChangeLog
index 71fbc2f547ba..cc4bf882d8b7 100644
--- a/libquadmath/ChangeLog
+++ b/libquadmath/ChangeLog
@@ -1,3 +1,8 @@
+2011-02-28  Jakub Jelinek  <jakub@redhat.com>
+
+	* printf/quadmath-printf.c (quadmath_snprintf): Make sure
+	that for size > 0 str is always zero terminated.
+
 2011-02-20  Jakub Jelinek  <jakub@redhat.com>
 
 	PR bootstrap/47827
diff --git a/libquadmath/printf/quadmath-printf.c b/libquadmath/printf/quadmath-printf.c
index 750dc246fcc8..b70f432cce02 100644
--- a/libquadmath/printf/quadmath-printf.c
+++ b/libquadmath/printf/quadmath-printf.c
@@ -256,7 +256,7 @@ quadmath_snprintf (char *str, size_t size, const char *format, ...)
 
   qfp.fp = NULL;
   qfp.str = str;
-  qfp.size = size;
+  qfp.size = size ? size - 1 : 0;
   qfp.len = 0;
   qfp.file_p = 0;
 
@@ -265,7 +265,7 @@ quadmath_snprintf (char *str, size_t size, const char *format, ...)
   else
     __quadmath_printf_fp (&qfp, &info, (const void *const *)&fpnum_addr2);
 
-  if (qfp.size)
+  if (size)
     *qfp.str = '\0';
 
   return qfp.len;