diff --git a/embed.fnc b/embed.fnc
index e9b05bfee02c..83439c3b59b9 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -5886,7 +5886,7 @@ ST	|void	|mem_log_common |enum mem_log_type mlt			\
 				|const UV typesize			\
 				|NN const char *type_name		\
 				|NULLOK const SV *sv			\
-				|Malloc_t oldalloc			\
+				|const Malloc_t oldalloc		\
 				|Malloc_t newalloc			\
 				|NN const char *filename		\
 				|const int linenumber			\
@@ -5921,7 +5921,7 @@ CTp	|Malloc_t|mem_log_realloc					\
 				|const UV n				\
 				|const UV typesize			\
 				|NN const char *type_name		\
-				|Malloc_t oldalloc			\
+				|const Malloc_t oldalloc		\
 				|Malloc_t newalloc			\
 				|NN const char *filename		\
 				|const int linenumber			\
diff --git a/proto.h b/proto.h
index e7b925ded912..44c4772615a6 100644
--- a/proto.h
+++ b/proto.h
@@ -9399,7 +9399,7 @@ S_xs_version_bootcheck(pTHX_ U32 items, U32 ax, const char *xs_p, STRLEN xs_len)
 
 # if defined(PERL_MEM_LOG) && !defined(PERL_MEM_LOG_NOIMPL)
 STATIC void
-S_mem_log_common(enum mem_log_type mlt, const UV n, const UV typesize, const char *type_name, const SV *sv, Malloc_t oldalloc, Malloc_t newalloc, const char *filename, const int linenumber, const char *funcname);
+S_mem_log_common(enum mem_log_type mlt, const UV n, const UV typesize, const char *type_name, const SV *sv, const Malloc_t oldalloc, Malloc_t newalloc, const char *filename, const int linenumber, const char *funcname);
 #   define PERL_ARGS_ASSERT_MEM_LOG_COMMON      \
         assert(type_name); assert(filename); assert(funcname)
 
@@ -9439,7 +9439,7 @@ Perl_mem_log_new_sv(const SV *sv, const char *filename, int linenumber, const ch
         assert(sv); assert(filename); assert(funcname)
 
 PERL_CALLCONV Malloc_t
-Perl_mem_log_realloc(const UV n, const UV typesize, const char *type_name, Malloc_t oldalloc, Malloc_t newalloc, const char *filename, const int linenumber, const char *funcname);
+Perl_mem_log_realloc(const UV n, const UV typesize, const char *type_name, const Malloc_t oldalloc, Malloc_t newalloc, const char *filename, const int linenumber, const char *funcname);
 # define PERL_ARGS_ASSERT_MEM_LOG_REALLOC       \
         assert(type_name); assert(filename); assert(funcname)
 
diff --git a/util.c b/util.c
index 3c1cae409afd..5cf604ade142 100644
--- a/util.c
+++ b/util.c
@@ -4885,7 +4885,7 @@ Perl_debug_hash_seed(pTHX_ bool via_debug_h)
 static void
 S_mem_log_common(enum mem_log_type mlt, const UV n, 
                  const UV typesize, const char *type_name, const SV *sv,
-                 Malloc_t oldalloc, Malloc_t newalloc,
+                 const Malloc_t oldalloc, Malloc_t newalloc,
                  const char *filename, const int linenumber,
                  const char *funcname)
 {
@@ -5033,7 +5033,7 @@ Perl_mem_log_alloc(const UV n, const UV typesize, const char *type_name,
 
 Malloc_t
 Perl_mem_log_realloc(const UV n, const UV typesize, const char *type_name,
-                     Malloc_t oldalloc, Malloc_t newalloc, 
+                     const Malloc_t oldalloc, Malloc_t newalloc,
                      const char *filename, const int linenumber, 
                      const char *funcname)
 {