diff --git a/ChangeLog b/ChangeLog
index be8ba294fb..b13a74ca2f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2010-02-11  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>
+
+	* sysdeps/s390/s390-64/utf8-utf16-z9.c: Disable hardware
+	instructions cu21 and cu24.  Add well-formedness checking
+	parameter and adjust the software implementation.
+	* sysdeps/s390/s390-64/utf16-utf32-z9.c: Likewise.
+
 2010-02-10  Ulrich Drepper  <drepper@redhat.com>
 
 	[BZ #11271]
diff --git a/sysdeps/s390/s390-64/utf16-utf32-z9.c b/sysdeps/s390/s390-64/utf16-utf32-z9.c
index 868dea68ca..14daf2118f 100644
--- a/sysdeps/s390/s390-64/utf16-utf32-z9.c
+++ b/sysdeps/s390/s390-64/utf16-utf32-z9.c
@@ -203,7 +203,10 @@ gconv_end (struct __gconv_step *data)
    swapping).  */
 #define BODY								\
   {									\
-    if (GLRO (dl_hwcap) & HWCAP_S390_ETF3EH)				\
+    /* The hardware instruction currently fails to report an error for	\
+       isolated low surrogates so we have to disable the instruction	\
+       until this gets resolved.  */					\
+    if (0) /* (GLRO (dl_hwcap) & HWCAP_S390_ETF3EH) */			\
       {									\
 	HARDWARE_CONVERT ("cu24 %0, %1, 1");				\
 	if (inptr != inend)						\
@@ -229,6 +232,12 @@ gconv_end (struct __gconv_step *data)
       }									\
     else								\
       {									\
+        /* An isolated low-surrogate was found.  This has to be         \
+	   considered ill-formed.  */					\
+        if (__builtin_expect (u1 >= 0xdc00, 0))				\
+	  {								\
+	    STANDARD_FROM_LOOP_ERR_HANDLER (2);				\
+	  }								\
 	/* It's a surrogate character.  At least the first word says	\
 	   it is.  */							\
 	if (__builtin_expect (inptr + 4 > inend, 0))			\
diff --git a/sysdeps/s390/s390-64/utf8-utf16-z9.c b/sysdeps/s390/s390-64/utf8-utf16-z9.c
index 531d3ebd4b..5f73f3c59e 100644
--- a/sysdeps/s390/s390-64/utf8-utf16-z9.c
+++ b/sysdeps/s390/s390-64/utf8-utf16-z9.c
@@ -345,9 +345,12 @@ gconv_end (struct __gconv_step *data)
    Operation.  */
 #define BODY								\
   {									\
-    if (GLRO (dl_hwcap) & HWCAP_S390_ETF3EH)				\
+    /* The hardware instruction currently fails to report an error for	\
+       isolated low surrogates so we have to disable the instruction	\
+       until this gets resolved.  */					\
+    if (0) /* (GLRO (dl_hwcap) & HWCAP_S390_ETF3EH) */			\
       {									\
-	HARDWARE_CONVERT ("cu21 %0, %1");				\
+	HARDWARE_CONVERT ("cu21 %0, %1, 1");				\
 	if (inptr != inend)						\
 	  {								\
 	    /* Check if the third byte is				\
@@ -388,7 +391,7 @@ gconv_end (struct __gconv_step *data)
 									\
 	outptr += 2;							\
       }									\
-    else if (c >= 0x0800 && c <= 0xd7ff)				\
+    else if ((c >= 0x0800 && c <= 0xd7ff) || c > 0xdfff)		\
       {									\
 	/* Three byte UTF-8 char.  */					\
 									\