diff --git a/configure.ac b/configure.ac
index 87640ae43b..1e80fba356 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1301,8 +1301,7 @@ AS_CASE([$with_jemalloc],
 
 AS_IF([test "$with_jemalloc" = "no"],
       [AS_CASE([$host],
-	       [*-freebsd*],[AC_MSG_ERROR([You cannot compile without jemalloc; jemalloc is the system allocator on FreeBSD])])
-       AC_CHECK_FUNCS([malloc_size malloc_usable_size])])
+	       [*-freebsd*],[AC_MSG_ERROR([You cannot compile without jemalloc; jemalloc is the system allocator on FreeBSD])])])
 
 AM_CONDITIONAL([HAVE_JEMALLOC], [test "$with_jemalloc" = "yes"])
 
diff --git a/lib/isc/include/isc/attributes.h b/lib/isc/include/isc/attributes.h
index abe615223e..f38a558552 100644
--- a/lib/isc/include/isc/attributes.h
+++ b/lib/isc/include/isc/attributes.h
@@ -80,3 +80,5 @@
 #define ISC_ATTR_MALLOC_DEALLOCATOR(deallocator)
 #define ISC_ATTR_MALLOC_DEALLOCATOR_IDX(deallocator, idx)
 #endif /* HAVE_FUNC_ATTRIBUTE_MALLOC */
+
+#define ISC_ATTR_UNUSED __attribute__((__unused__))
diff --git a/lib/isc/jemalloc_shim.h b/lib/isc/jemalloc_shim.h
index 493bf5ffc0..9f7bc9db31 100644
--- a/lib/isc/jemalloc_shim.h
+++ b/lib/isc/jemalloc_shim.h
@@ -27,67 +27,6 @@ const char *malloc_conf = NULL;
 #define MALLOCX_TCACHE_NONE (0)
 #define MALLOCX_ARENA(a)    (0)
 
-#if defined(HAVE_MALLOC_SIZE) || defined(HAVE_MALLOC_USABLE_SIZE)
-
-#include <stdlib.h>
-
-static inline void *
-mallocx(size_t size, int flags) {
-	UNUSED(flags);
-
-	return (malloc(size));
-}
-
-static inline void
-sdallocx(void *ptr, size_t size, int flags) {
-	UNUSED(size);
-	UNUSED(flags);
-
-	free(ptr);
-}
-
-static inline void *
-rallocx(void *ptr, size_t size, int flags) {
-	UNUSED(flags);
-	REQUIRE(size != 0);
-
-	return (realloc(ptr, size));
-}
-
-#ifdef HAVE_MALLOC_SIZE
-
-#include <malloc/malloc.h>
-
-static inline size_t
-sallocx(void *ptr, int flags) {
-	UNUSED(flags);
-
-	return (malloc_size(ptr));
-}
-
-#elif HAVE_MALLOC_USABLE_SIZE
-
-#ifdef __DragonFly__
-/*
- * On DragonFly BSD 'man 3 malloc' advises us to include the following
- * header to have access to malloc_usable_size().
- */
-#include <malloc_np.h>
-#else
-#include <malloc.h>
-#endif
-
-static inline size_t
-sallocx(void *ptr, int flags) {
-	UNUSED(flags);
-
-	return (malloc_usable_size(ptr));
-}
-
-#endif /* HAVE_MALLOC_SIZE */
-
-#else /* defined(HAVE_MALLOC_SIZE) || defined (HAVE_MALLOC_USABLE_SIZE) */
-
 #include <stdlib.h>
 
 typedef union {
@@ -111,21 +50,16 @@ mallocx(size_t size, int flags) {
 }
 
 static inline void
-sdallocx(void *ptr, size_t size, int flags) {
+sdallocx(void *ptr, size_t size ISC_ATTR_UNUSED, int flags ISC_ATTR_UNUSED) {
 	size_info *si = &(((size_info *)ptr)[-1]);
 
-	UNUSED(size);
-	UNUSED(flags);
-
 	free(si);
 }
 
 static inline size_t
-sallocx(void *ptr, int flags) {
+sallocx(void *ptr, int flags ISC_ATTR_UNUSED) {
 	size_info *si = &(((size_info *)ptr)[-1]);
 
-	UNUSED(flags);
-
 	return (si[0].size);
 }
 
@@ -144,6 +78,4 @@ rallocx(void *ptr, size_t size, int flags) {
 	return (ptr);
 }
 
-#endif /* defined(HAVE_MALLOC_SIZE) || defined (HAVE_MALLOC_USABLE_SIZE) */
-
 #endif /* !defined(HAVE_JEMALLOC) */