diff --git a/iconvdata/Makefile b/iconvdata/Makefile
index c83962f351..71ddef09db 100644
--- a/iconvdata/Makefile
+++ b/iconvdata/Makefile
@@ -73,7 +73,7 @@ modules.so := $(addsuffix .so, $(modules))
 ifeq (yes,$(build-shared))
 tests = bug-iconv1 bug-iconv2 tst-loading tst-e2big tst-iconv4 bug-iconv4 \
 	tst-iconv6 bug-iconv5 bug-iconv6 tst-iconv7 bug-iconv8 bug-iconv9 \
-	bug-iconv10 bug-iconv11 bug-iconv12
+	bug-iconv10 bug-iconv11 bug-iconv12 tst-iconv-big5-hkscs-to-2ucs4
 ifeq ($(have-thread-library),yes)
 tests += bug-iconv3
 endif
@@ -340,3 +340,7 @@ tst-tables-clean:
 
 $(objpfx)gconv-modules: gconv-modules
 	cat $(sysdeps-gconv-modules) $^ > $@
+
+# Test requires BIG5HKSCS.
+$(objpfx)tst-iconv-big5-hkscs-to-2ucs4.out: $(objpfx)gconv-modules \
+			  $(addprefix $(objpfx),BIG5HKSCS.so)
diff --git a/iconvdata/big5hkscs.c b/iconvdata/big5hkscs.c
index 01fcfeba76..ef325119b1 100644
--- a/iconvdata/big5hkscs.c
+++ b/iconvdata/big5hkscs.c
@@ -17895,6 +17895,9 @@ static struct
 	else								      \
 	  ++inptr;							      \
       }									      \
+    else								      \
+      /* Clear the queue and proceed to output the saved character.  */	      \
+      *statep = 0;							      \
 									      \
     put32 (outptr, ch);							      \
     outptr += 4;							      \
diff --git a/iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c b/iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c
new file mode 100644
index 0000000000..a10b8fefff
--- /dev/null
+++ b/iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c
@@ -0,0 +1,146 @@
+/* Verify the BIG5HKSCS outputs that generate 2 wchar_t's (Bug 25734).
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <string.h>
+#include <locale.h>
+#include <wchar.h>
+#include <support/check.h>
+#include <support/support.h>
+
+/* A few BIG5-HKSCS characters map in two unicode code points.
+   They are:
+   /x88/x62 => <U00CA><U0304>
+   /x88/x64 => <U00CA><U030C>
+   /x88/xa3 => <U00EA><U0304>
+   /x88/xa5 => <U00EA><U030C>
+   Each of these is special cased in iconvdata/big5hkscs.c.
+   This test ensures that we correctly reset the shift state after
+   outputting any of these characters.  We do this by converting
+   each them followed by converting an ASCII character.  If we fail
+   to reset the shift state (bug 25734) then we'll see the last
+   character in the queue output again.  */
+
+/* Each test has  name, input bytes, and expected wide character
+   output.  */
+struct testdata {
+  const char *name;
+  const char input[3];
+  wchar_t expected[3];
+};
+
+/* In BIG5-HKSCS (2008) there are 4 characters that generate multiple
+   wide characters.  */
+struct testdata tests[4] = {
+  /* <H-8862>X => <U+00CA><U+0304>X */
+  { "<H-8862>", "\x88\x62\x58", { 0x00CA, 0x0304, 0x0058 } },
+  /* <H-8864>X => <U+00CA><U+030C>X */
+  { "<H-8864>", "\x88\x64\x58", { 0x00CA, 0x030C, 0x0058 } },
+  /* <H-88A3>X => <U+00EA><U+0304>X */
+  { "<H-88A3>", "\x88\xa3\x58", { 0x00EA, 0x0304, 0x0058 } },
+  /* <H-88A5>X => <U+00EA><U+030C>X */
+  { "<H-88A5>", "\x88\xa5\x58", { 0x00EA, 0x030C, 0x0058 } }
+};
+
+/* Each test is of the form:
+   - Translate first code sequence (two bytes)
+   - Translate second (zero bytes)
+   - Translate the third (one byte).  */
+static int
+check_conversion (struct testdata test)
+{
+  wchar_t wc;
+  mbstate_t st;
+  size_t ret;
+  const char *mbs = test.input;
+  int consumed = 0;
+  /* Input is always 3 bytes long.  */
+  int inlen = 3;
+
+  memset (&st, 0, sizeof (st));
+  /* First conversion: Consumes first 2 bytes.  */
+  ret = mbrtowc (&wc, mbs, inlen - consumed, &st); 
+  if (ret != 2)
+    {
+      printf ("error: First conversion consumed only %zd bytes.\n", ret);
+      return 1;
+    }
+  /* Advance the two consumed bytes.  */
+  mbs += ret;
+  consumed += ret;
+  if (wc != test.expected[0])
+    {
+      printf ("error: Result of first conversion was wrong.\n");
+      return 1;
+    }
+  /* Second conversion: Consumes 0 bytes.  */
+  ret = mbrtowc (&wc, mbs, inlen - consumed, &st); 
+  if (ret != 0)
+    {
+      printf ("error: Second conversion consumed only %zd bytes.\n", ret);
+      return 1;
+    }
+  /* Advance the zero consumed bytes.  */
+  mbs += ret;
+  consumed += ret;
+  if (wc != test.expected[1])
+    {
+      printf ("error: Result of second conversion was wrong.\n");
+      return 1;
+    }
+  /* Third conversion: Consumes 1 byte (it's an ASCII character).  */
+  ret = mbrtowc (&wc, mbs, inlen - consumed, &st); 
+  if (ret != 1)
+    {
+      printf ("error: Third conversion consumed only %zd bytes.\n", ret);
+      return 1;
+    }
+  /* Don't advance any bytes becuase none were consumed.  */
+  if (wc != test.expected[2])
+    {
+      printf ("error: Result of first conversion was wrong.\n");
+      return 1;
+    }
+  /* Success.  */
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  int err = 0;
+  /* Testing BIG5-HKSCS.  */
+  xsetlocale (LC_ALL, "zh_HK.BIG5-HKSCS");
+
+  /* Run all the special conversions.  */
+  for (int i = 0; i < (sizeof (tests) / sizeof (struct testdata)); i++)
+    {
+      printf ("Running test for %s\n", tests[i].name);
+      err += check_conversion (tests[i]);
+      if (err > 0)
+	printf ("Test %s failed.\n", tests[i].name);
+    }
+
+  /* Fail if any conversion had an error.  */
+  if (err > 0)
+    FAIL_EXIT1 ("One of the conversions failed.");
+
+  return 0; 
+}
+
+#include <support/test-driver.c>
