diff --git a/include/alloc_buffer.h b/include/alloc_buffer.h
index 5dcd009405..17acada715 100644
--- a/include/alloc_buffer.h
+++ b/include/alloc_buffer.h
@@ -113,10 +113,8 @@ enum
   };
 
 /* Internal function.  Terminate the process using __libc_fatal.  */
-void __libc_alloc_buffer_create_failure (void *start, size_t size);
-#ifndef _ISOMAC
-libc_hidden_proto (__libc_alloc_buffer_create_failure)
-#endif
+void __libc_alloc_buffer_create_failure (void *start, size_t size)
+  attribute_hidden;
 
 /* Create a new allocation buffer.  The byte range from START to START
    + SIZE - 1 must be valid, and the allocation buffer allocates
@@ -134,10 +132,7 @@ alloc_buffer_create (void *start, size_t size)
 
 /* Internal function.  See alloc_buffer_allocate below.  */
 struct alloc_buffer __libc_alloc_buffer_allocate (size_t size, void **pptr)
-  __attribute__ ((nonnull (2)));
-#ifndef _ISOMAC
-libc_hidden_proto (__libc_alloc_buffer_allocate)
-#endif
+  attribute_hidden __attribute__ ((nonnull (2)));
 
 /* Allocate a buffer of SIZE bytes using malloc.  The returned buffer
    is in a failed state if malloc fails.  *PPTR points to the start of
@@ -338,10 +333,7 @@ __alloc_buffer_next (struct alloc_buffer *buf, size_t align)
 void * __libc_alloc_buffer_alloc_array (struct alloc_buffer *buf,
 					size_t size, size_t align,
 					size_t count)
-  __attribute__ ((nonnull (1)));
-#ifndef _ISOMAC
-libc_hidden_proto (__libc_alloc_buffer_alloc_array)
-#endif
+  attribute_hidden __attribute__ ((nonnull (1)));
 
 /* Obtain a TYPE * pointer to an array of COUNT objects in BUF of
    TYPE.  Consume these bytes from the buffer.  Return NULL and mark
@@ -357,10 +349,7 @@ libc_hidden_proto (__libc_alloc_buffer_alloc_array)
 /* Internal function.  See alloc_buffer_copy_bytes below.  */
 struct alloc_buffer __libc_alloc_buffer_copy_bytes (struct alloc_buffer,
 						    const void *, size_t)
-  __attribute__ ((nonnull (2)));
-#ifndef _ISOMAC
-libc_hidden_proto (__libc_alloc_buffer_copy_bytes)
-#endif
+  attribute_hidden __attribute__ ((nonnull (2)));
 
 /* Copy SIZE bytes starting at SRC into the buffer.  If there is not
    enough room in the buffer, the buffer is marked as failed.  No
@@ -374,10 +363,7 @@ alloc_buffer_copy_bytes (struct alloc_buffer *buf, const void *src, size_t size)
 /* Internal function.  See alloc_buffer_copy_string below.  */
 struct alloc_buffer __libc_alloc_buffer_copy_string (struct alloc_buffer,
 						     const char *)
-  __attribute__ ((nonnull (2)));
-#ifndef _ISOMAC
-libc_hidden_proto (__libc_alloc_buffer_copy_string)
-#endif
+  attribute_hidden __attribute__ ((nonnull (2)));
 
 /* Copy the string at SRC into the buffer, including its null
    terminator.  If there is not enough room in the buffer, the buffer
diff --git a/malloc/Makefile b/malloc/Makefile
index c1db3347d8..4751366496 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -34,7 +34,6 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
 	 tst-mallocfork3 \
 	 tst-interpose-nothread \
 	 tst-interpose-thread \
-	 tst-alloc_buffer \
 	 tst-free-errno \
 	 tst-malloc-tcache-leak \
 	 tst-malloc_info tst-mallinfo2 \
@@ -57,7 +56,10 @@ ifeq ($(have-GLIBC_2.23)$(build-shared),yesyes)
 tests += tst-mallocstate tst-compathooks-off tst-compathooks-on
 endif
 
-tests-internal := tst-scratch_buffer
+tests-internal := \
+  tst-alloc_buffer \
+  tst-scratch_buffer \
+  # tests-internal
 
 # The dynarray framework is only available inside glibc.
 tests-internal += \
diff --git a/malloc/Versions b/malloc/Versions
index c763395c6d..011b6a5a85 100644
--- a/malloc/Versions
+++ b/malloc/Versions
@@ -88,13 +88,6 @@ libc {
     __libc_dynarray_finalize;
     __libc_dynarray_resize;
     __libc_dynarray_resize_clear;
-
-    # struct alloc_buffer support
-    __libc_alloc_buffer_alloc_array;
-    __libc_alloc_buffer_allocate;
-    __libc_alloc_buffer_copy_bytes;
-    __libc_alloc_buffer_copy_string;
-    __libc_alloc_buffer_create_failure;
   }
 }
 
diff --git a/malloc/alloc_buffer_alloc_array.c b/malloc/alloc_buffer_alloc_array.c
index 018d07061a..739934d9fd 100644
--- a/malloc/alloc_buffer_alloc_array.c
+++ b/malloc/alloc_buffer_alloc_array.c
@@ -43,4 +43,3 @@ __libc_alloc_buffer_alloc_array (struct alloc_buffer *buf, size_t element_size,
       return NULL;
     }
 }
-libc_hidden_def (__libc_alloc_buffer_alloc_array)
diff --git a/malloc/alloc_buffer_allocate.c b/malloc/alloc_buffer_allocate.c
index 7f1e083a7c..8b05f55a3d 100644
--- a/malloc/alloc_buffer_allocate.c
+++ b/malloc/alloc_buffer_allocate.c
@@ -33,4 +33,3 @@ __libc_alloc_buffer_allocate (size_t size, void **pptr)
   else
     return alloc_buffer_create (*pptr, size);
 }
-libc_hidden_def (__libc_alloc_buffer_allocate)
diff --git a/malloc/alloc_buffer_copy_bytes.c b/malloc/alloc_buffer_copy_bytes.c
index 397f6a734f..2e261da02e 100644
--- a/malloc/alloc_buffer_copy_bytes.c
+++ b/malloc/alloc_buffer_copy_bytes.c
@@ -31,4 +31,3 @@ __libc_alloc_buffer_copy_bytes (struct alloc_buffer buf,
     memcpy (ptr, src, len);
   return buf;
 }
-libc_hidden_def (__libc_alloc_buffer_copy_bytes)
diff --git a/malloc/alloc_buffer_copy_string.c b/malloc/alloc_buffer_copy_string.c
index a334bd359d..711fbcf695 100644
--- a/malloc/alloc_buffer_copy_string.c
+++ b/malloc/alloc_buffer_copy_string.c
@@ -27,4 +27,3 @@ __libc_alloc_buffer_copy_string (struct alloc_buffer buf, const char *src)
 {
   return __libc_alloc_buffer_copy_bytes (buf, src, strlen (src) + 1);
 }
-libc_hidden_def (__libc_alloc_buffer_copy_string)
diff --git a/malloc/alloc_buffer_create_failure.c b/malloc/alloc_buffer_create_failure.c
index 77ce9378ce..c9557cae5b 100644
--- a/malloc/alloc_buffer_create_failure.c
+++ b/malloc/alloc_buffer_create_failure.c
@@ -28,4 +28,3 @@ __libc_alloc_buffer_create_failure (void *start, size_t size)
               size);
   __libc_fatal (buf);
 }
-libc_hidden_def (__libc_alloc_buffer_create_failure)
diff --git a/malloc/tst-alloc_buffer.c b/malloc/tst-alloc_buffer.c
index 567cb1b172..5e06b5e91c 100644
--- a/malloc/tst-alloc_buffer.c
+++ b/malloc/tst-alloc_buffer.c
@@ -16,6 +16,10 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+/* Note: This test exercises the (identical) copy of the
+   <alloc_buffer.h> in libsupport, not libc.so, because the latter has
+   hidden visibility and cannot be tested from the outside.  */
+
 #include <arpa/inet.h>
 #include <alloc_buffer.h>
 #include <stdio.h>
diff --git a/nss/Makefile b/nss/Makefile
index 3a9ea065ac..e9d2d42f72 100644
--- a/nss/Makefile
+++ b/nss/Makefile
@@ -179,9 +179,9 @@ rtld-tests-LDFLAGS += -Wl,--dynamic-list=nss_test.ver
 libof-nss_test1 = extramodules
 libof-nss_test2 = extramodules
 libof-nss_test_errno = extramodules
-$(objpfx)/libnss_test1.so: $(objpfx)nss_test1.os $(link-libc-deps)
+$(objpfx)/libnss_test1.so: $(objpfx)nss_test1.os $(libsupport) $(link-libc-deps)
 	$(build-module)
-$(objpfx)/libnss_test2.so: $(objpfx)nss_test2.os $(link-libc-deps)
+$(objpfx)/libnss_test2.so: $(objpfx)nss_test2.os $(libsupport) $(link-libc-deps)
 	$(build-module)
 $(objpfx)/libnss_test_errno.so: $(objpfx)nss_test_errno.os $(link-libc-deps)
 	$(build-module)
diff --git a/support/Makefile b/support/Makefile
index c2873c4b24..e36710adc6 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -41,6 +41,7 @@ libsupport-routines = \
   resolv_response_context_free \
   resolv_test \
   set_fortify_handler \
+  support-alloc_buffer \
   support-open-dev-null-range \
   support-xfstat \
   support-xfstat-time64 \
diff --git a/support/support-alloc_buffer.c b/support/support-alloc_buffer.c
new file mode 100644
index 0000000000..11f967295c
--- /dev/null
+++ b/support/support-alloc_buffer.c
@@ -0,0 +1,26 @@
+/* Make <alloc_buffer.h> available to tests.
+   Copyright (C) 2023 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/>.  */
+
+/* The implementation in libc.so has hidden visibility and is
+   therefore not usable.  */
+
+#include <malloc/alloc_buffer_alloc_array.c>
+#include <malloc/alloc_buffer_allocate.c>
+#include <malloc/alloc_buffer_copy_bytes.c>
+#include <malloc/alloc_buffer_copy_string.c>
+#include <malloc/alloc_buffer_create_failure.c>
