diff --git a/0001-block_peek-memory_peek-Use-bytes-for-return-buffer.patch b/0001-block_peek-memory_peek-Use-bytes-for-return-buffer.patch
new file mode 100644
index 0000000..f3b93af
--- /dev/null
+++ b/0001-block_peek-memory_peek-Use-bytes-for-return-buffer.patch
@@ -0,0 +1,74 @@
+From 29709872404fad20a9822c43a831f30b7b09f34a Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Sun, 19 Jan 2020 12:58:17 +0000
+Subject: [PATCH 1/3] block_peek, memory_peek: Use bytes for return buffer.
+
+Strings are immutable in modern OCaml.
+---
+ libvirt/libvirt.ml          | 4 ++--
+ libvirt/libvirt.mli         | 4 ++--
+ libvirt/libvirt_c_oneoffs.c | 4 ++--
+ 3 files changed, 6 insertions(+), 6 deletions(-)
+
+diff --git a/libvirt/libvirt.ml b/libvirt/libvirt.ml
+index 7f9d0e4..bdb9460 100644
+--- a/libvirt/libvirt.ml
++++ b/libvirt/libvirt.ml
+@@ -731,8 +731,8 @@ struct
+   external migrate : [>`W] t -> [>`W] Connect.t -> migrate_flag list -> ?dname:string -> ?uri:string -> ?bandwidth:int -> unit -> rw t = "ocaml_libvirt_domain_migrate_bytecode" "ocaml_libvirt_domain_migrate_native"
+   external block_stats : [>`R] t -> string -> block_stats = "ocaml_libvirt_domain_block_stats"
+   external interface_stats : [>`R] t -> string -> interface_stats = "ocaml_libvirt_domain_interface_stats"
+-  external block_peek : [>`W] t -> string -> int64 -> int -> string -> int -> unit = "ocaml_libvirt_domain_block_peek_bytecode" "ocaml_libvirt_domain_block_peek_native"
+-  external memory_peek : [>`W] t -> memory_flag list -> int64 -> int -> string -> int -> unit = "ocaml_libvirt_domain_memory_peek_bytecode" "ocaml_libvirt_domain_memory_peek_native"
++  external block_peek : [>`W] t -> string -> int64 -> int -> bytes -> int -> unit = "ocaml_libvirt_domain_block_peek_bytecode" "ocaml_libvirt_domain_block_peek_native"
++  external memory_peek : [>`W] t -> memory_flag list -> int64 -> int -> bytes -> int -> unit = "ocaml_libvirt_domain_memory_peek_bytecode" "ocaml_libvirt_domain_memory_peek_native"
+ 
+   external get_all_domain_stats : [>`R] Connect.t -> stats_type list -> get_all_domain_stats_flag list -> domain_stats_record array = "ocaml_libvirt_domain_get_all_domain_stats"
+ 
+diff --git a/libvirt/libvirt.mli b/libvirt/libvirt.mli
+index 0d74199..7900392 100644
+--- a/libvirt/libvirt.mli
++++ b/libvirt/libvirt.mli
+@@ -708,7 +708,7 @@ sig
+   val interface_stats : [>`R] t -> string -> interface_stats
+     (** Returns network interface stats. *)
+ 
+-  val block_peek : [>`W] t -> string -> int64 -> int -> string -> int -> unit
++  val block_peek : [>`W] t -> string -> int64 -> int -> bytes -> int -> unit
+     (** [block_peek dom path offset size buf boff] reads [size] bytes at
+ 	[offset] in the domain's [path] block device.
+ 
+@@ -717,7 +717,7 @@ sig
+ 
+ 	See also {!max_peek}. *)
+   val memory_peek : [>`W] t -> memory_flag list -> int64 -> int ->
+-    string -> int -> unit
++    bytes -> int -> unit
+     (** [memory_peek dom Virtual offset size] reads [size] bytes
+ 	at [offset] in the domain's virtual memory.
+ 
+diff --git a/libvirt/libvirt_c_oneoffs.c b/libvirt/libvirt_c_oneoffs.c
+index 40384e8..8468c73 100644
+--- a/libvirt/libvirt_c_oneoffs.c
++++ b/libvirt/libvirt_c_oneoffs.c
+@@ -1057,7 +1057,7 @@ ocaml_libvirt_domain_block_peek_native (value domv, value pathv, value offsetv,
+   const char *path = String_val (pathv);
+   unsigned long long offset = Int64_val (offsetv);
+   size_t size = Int_val (sizev);
+-  char *buffer = String_val (bufferv);
++  unsigned char *buffer = Bytes_val (bufferv);
+   int boff = Int_val (boffv);
+   int r;
+ 
+@@ -1089,7 +1089,7 @@ ocaml_libvirt_domain_memory_peek_native (value domv, value flagsv, value offsetv
+   int flags = 0;
+   unsigned long long offset = Int64_val (offsetv);
+   size_t size = Int_val (sizev);
+-  char *buffer = String_val (bufferv);
++  unsigned char *buffer = Bytes_val (bufferv);
+   int boff = Int_val (boffv);
+   int r;
+ 
+-- 
+2.24.1
+
diff --git a/0002-String_val-returns-const-char-in-OCaml-4.10.patch b/0002-String_val-returns-const-char-in-OCaml-4.10.patch
new file mode 100644
index 0000000..4f547cb
--- /dev/null
+++ b/0002-String_val-returns-const-char-in-OCaml-4.10.patch
@@ -0,0 +1,113 @@
+From 3705b9bdcd04dc86474c62e1c8dd8759669842bc Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Sun, 19 Jan 2020 12:59:09 +0000
+Subject: [PATCH 2/3] String_val returns const char * in OCaml 4.10.
+
+This should be compatible with earlier versions of OCaml
+too since we are just assigning a char * to a const char *.
+---
+ libvirt/generator.pl        | 14 +++++++-------
+ libvirt/libvirt_c_oneoffs.c |  6 +++---
+ 2 files changed, 10 insertions(+), 10 deletions(-)
+
+diff --git a/libvirt/generator.pl b/libvirt/generator.pl
+index ac3dd65..aff371b 100755
+--- a/libvirt/generator.pl
++++ b/libvirt/generator.pl
+@@ -593,7 +593,7 @@ sub gen_c_code
+     } elsif ($sig =~ /^(\w+), string : unit$/) {
+ 	"\
+   " . gen_unpack_args ($1) . "
+-  char *str = String_val (strv);
++  const char *str = String_val (strv);
+   int r;
+ 
+   NONBLOCKING (r = $c_name ($1, str));
+@@ -605,7 +605,7 @@ sub gen_c_code
+ 	"\
+   CAMLlocal1 (rv);
+   " . gen_unpack_args ($1) . "
+-  char *str = String_val (strv);
++  const char *str = String_val (strv);
+   int r;
+ 
+   NONBLOCKING (r = $c_name ($1, str, 0));
+@@ -618,7 +618,7 @@ sub gen_c_code
+ 	"\
+   CAMLlocal1 (rv);
+   " . gen_unpack_args ($1) . "
+-  char *str = String_val (strv);
++  const char *str = String_val (strv);
+   $c_ret_type r;
+ 
+   NONBLOCKING (r = $c_name ($1, str));
+@@ -633,7 +633,7 @@ sub gen_c_code
+ 	"\
+   CAMLlocal1 (rv);
+   " . gen_unpack_args ($1) . "
+-  char *str = String_val (strv);
++  const char *str = String_val (strv);
+   $c_ret_type r;
+ 
+   NONBLOCKING (r = $c_name ($1, str, 0));
+@@ -648,7 +648,7 @@ sub gen_c_code
+ 	"\
+   CAMLlocal1 (rv);
+   " . gen_unpack_args ($1) . "
+-  char *str = String_val (strv);
++  const char *str = String_val (strv);
+   unsigned int u = Int_val (uv);
+   $c_ret_type r;
+ 
+@@ -735,7 +735,7 @@ sub gen_c_code
+ 	"\
+   CAMLlocal2 (rv, connv);
+   " . gen_unpack_args ($1) . "
+-  char *str = String_val (strv);
++  const char *str = String_val (strv);
+   $c_ret_type r;
+ 
+   NONBLOCKING (r = $c_name ($1, str));
+@@ -751,7 +751,7 @@ sub gen_c_code
+ 	"\
+   CAMLlocal2 (rv, connv);
+   " . gen_unpack_args ($1) . "
+-  char *str = String_val (strv);
++  const char *str = String_val (strv);
+   $c_ret_type r;
+ 
+   NONBLOCKING (r = $c_name ($1, str, 0));
+diff --git a/libvirt/libvirt_c_oneoffs.c b/libvirt/libvirt_c_oneoffs.c
+index 8468c73..fc2ac13 100644
+--- a/libvirt/libvirt_c_oneoffs.c
++++ b/libvirt/libvirt_c_oneoffs.c
+@@ -601,7 +601,7 @@ ocaml_libvirt_domain_set_scheduler_parameters (value domv, value paramsv)
+   int nparams = Wosize_val (paramsv);
+   virSchedParameterPtr params;
+   int r, i;
+-  char *name;
++  const char *name;
+ 
+   params = malloc (sizeof (*params) * nparams);
+   if (params == NULL)
+@@ -1005,7 +1005,7 @@ ocaml_libvirt_domain_block_stats (value domv, value pathv)
+   CAMLparam2 (domv, pathv);
+   CAMLlocal2 (rv,v);
+   virDomainPtr dom = Domain_val (domv);
+-  char *path = String_val (pathv);
++  const char *path = String_val (pathv);
+   struct _virDomainBlockStats stats;
+   int r;
+ 
+@@ -1028,7 +1028,7 @@ ocaml_libvirt_domain_interface_stats (value domv, value pathv)
+   CAMLparam2 (domv, pathv);
+   CAMLlocal2 (rv,v);
+   virDomainPtr dom = Domain_val (domv);
+-  char *path = String_val (pathv);
++  const char *path = String_val (pathv);
+   struct _virDomainInterfaceStats stats;
+   int r;
+ 
+-- 
+2.24.1
+
diff --git a/0003-Don-t-try-to-memcpy-into-a-String_val.patch b/0003-Don-t-try-to-memcpy-into-a-String_val.patch
new file mode 100644
index 0000000..720787f
--- /dev/null
+++ b/0003-Don-t-try-to-memcpy-into-a-String_val.patch
@@ -0,0 +1,68 @@
+From 3d3d6af425d369200a7a62a127adf640d94a38a3 Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Sun, 19 Jan 2020 13:02:16 +0000
+Subject: [PATCH 3/3] Don't try to memcpy into a String_val.
+
+In OCaml 4.10 String_val returns const char *, so we cannot use it as
+the destination for memcpy.  Use Bytes_val instead.
+---
+ libvirt/generator.pl        | 2 +-
+ libvirt/libvirt_c_oneoffs.c | 8 ++++----
+ 2 files changed, 5 insertions(+), 5 deletions(-)
+
+diff --git a/libvirt/generator.pl b/libvirt/generator.pl
+index aff371b..463a19b 100755
+--- a/libvirt/generator.pl
++++ b/libvirt/generator.pl
+@@ -440,7 +440,7 @@ sub gen_c_code
+ 
+   /* UUIDs are byte arrays with a fixed length. */
+   rv = caml_alloc_string (VIR_UUID_BUFLEN);
+-  memcpy (String_val (rv), uuid, VIR_UUID_BUFLEN);
++  memcpy (Bytes_val (rv), uuid, VIR_UUID_BUFLEN);
+   CAMLreturn (rv);
+ "
+     } elsif ($sig =~ /^(\w+) : uuid string$/) {
+diff --git a/libvirt/libvirt_c_oneoffs.c b/libvirt/libvirt_c_oneoffs.c
+index fc2ac13..e8472b7 100644
+--- a/libvirt/libvirt_c_oneoffs.c
++++ b/libvirt/libvirt_c_oneoffs.c
+@@ -394,7 +394,7 @@ ocaml_libvirt_connect_call_auth_default_callback (value listv)
+       elemv = caml_alloc (2, 0);
+       if (cred->result != NULL && cred->resultlen > 0) {
+         v = caml_alloc_string (cred->resultlen);
+-        memcpy (String_val (v), cred->result, cred->resultlen);
++        memcpy (Bytes_val (v), cred->result, cred->resultlen);
+         optv = caml_alloc (1, 0);
+         Store_field (optv, 0, v);
+       } else
+@@ -715,7 +715,7 @@ ocaml_libvirt_domain_get_vcpus (value domv, value maxinfov, value maplenv)
+ 
+   /* Copy the bitmap. */
+   strv = caml_alloc_string (maxinfo * maplen);
+-  memcpy (String_val (strv), cpumaps, maxinfo * maplen);
++  memcpy (Bytes_val (strv), cpumaps, maxinfo * maplen);
+ 
+   /* Allocate the tuple and return it. */
+   rv = caml_alloc_tuple (3);
+@@ -900,7 +900,7 @@ ocaml_libvirt_domain_get_all_domain_stats (value connv,
+      */
+     v = caml_alloc_string (VIR_UUID_BUFLEN);
+     virDomainGetUUID (rstats[i]->dom, uuid);
+-    memcpy (String_val (v), uuid, VIR_UUID_BUFLEN);
++    memcpy (Bytes_val (v), uuid, VIR_UUID_BUFLEN);
+     Store_field (dsv, 0, v);
+ 
+     tpv = caml_alloc (rstats[i]->nparams, 0); /* typed_param array */
+@@ -1646,7 +1646,7 @@ ocaml_libvirt_secret_get_value (value secv)
+   CHECK_ERROR (secval == NULL, "virSecretGetValue");
+ 
+   rv = caml_alloc_string (size);
+-  memcpy (String_val (rv), secval, size);
++  memcpy (Bytes_val (rv), secval, size);
+   free (secval);
+ 
+   CAMLreturn (rv);
+-- 
+2.24.1
+
diff --git a/ocaml-libvirt.spec b/ocaml-libvirt.spec
index 8b7b84c..dbbf946 100644
--- a/ocaml-libvirt.spec
+++ b/ocaml-libvirt.spec
@@ -11,6 +11,11 @@ Source0:        http://libvirt.org/sources/ocaml/%{name}-%{version}.tar.gz
 # Upstream commit 75b13978f85b32c7a121aa289d8ebf41ba14ee5a.
 Patch1:         0001-Make-const-the-return-value-of-caml_named_value.patch
 
+# Fixes for OCaml 4.10, sent upstream 2020-01-19.
+Patch2:         0001-block_peek-memory_peek-Use-bytes-for-return-buffer.patch
+Patch3:         0002-String_val-returns-const-char-in-OCaml-4.10.patch
+Patch4:         0003-Don-t-try-to-memcpy-into-a-String_val.patch
+
 BuildRequires:  ocaml >= 3.10.0
 BuildRequires:  ocaml-ocamldoc
 BuildRequires:  ocaml-findlib-devel