diff --git a/daemon/Makefile.am b/daemon/Makefile.am
index bb2e58d01..b30153bab 100644
--- a/daemon/Makefile.am
+++ b/daemon/Makefile.am
@@ -374,9 +374,11 @@ OCAML_LIBS = \
 	-lmlstdutils \
 	-lmlaugeas \
 	-lmlhivex \
-	-lcamlstr \
-	-lunix \
-	-l$(CAMLRUN) -ldl -lm
+	-l$(CAMLSTR) \
+	-l$(CAMLUNIX) \
+	-l$(CAMLRUN) \
+	$(LIBZSTD_LIBS) \
+	-ldl -lm
 
 CLEANFILES += camldaemon.o
 
diff --git a/m4/guestfs-libraries.m4 b/m4/guestfs-libraries.m4
index 29d012a37..18c4cd307 100644
--- a/m4/guestfs-libraries.m4
+++ b/m4/guestfs-libraries.m4
@@ -248,6 +248,9 @@ PKG_CHECK_MODULES([PCRE2], [libpcre2-8], [], [
     PCRE_LIBS=`$PCRE2_CONFIG --libs8`
 ])
 
+dnl Check for zstd (required since OCaml 5.1)
+PKG_CHECK_MODULES([LIBZSTD], [libzstd])
+
 dnl Check for Augeas >= 1.2.0 (required).
 PKG_CHECK_MODULES([AUGEAS],[augeas >= 1.2.0])
 
diff --git a/m4/guestfs-ocaml.m4 b/m4/guestfs-ocaml.m4
index 39a8346f3..25b06408c 100644
--- a/m4/guestfs-ocaml.m4
+++ b/m4/guestfs-ocaml.m4
@@ -122,6 +122,47 @@ if test "x$enable_daemon" = "xyes"; then
         AC_MSG_ERROR([could not find or link to libasmrun or libcamlrun])
     fi
     AC_SUBST([CAMLRUN])
+
+    dnl OCaml 5.1 changed -lcamlstr to -lcamlstrnat / -lcamlstrbyt
+    dnl and -lunix to -lunixnat / -lunixbyt so we need to detect
+    dnl the new or old libraries.  As above we cannot use AC_CHECK_LIB.
+    AC_MSG_CHECKING([how to link the daemon with -lcamlstr*])
+    if test "x$OCAMLOPT" != "xno"; then
+        choices="camlstrnat camlstr"
+    else
+        choices="camlstrbyt camlstr"
+    fi
+    for f in $choices; do
+        if test -f "$OCAMLLIB/lib$f.a"; then
+            CAMLSTR=$f
+            break
+        fi
+    done
+    if test "x$CAMLSTR" != "x"; then
+        AC_MSG_RESULT([$CAMLSTR])
+    else
+        AC_MSG_ERROR([could not find or link to -lcamlstr*])
+    fi
+    AC_SUBST([CAMLSTR])
+
+    AC_MSG_CHECKING([how to link the daemon with -lunix*])
+    if test "x$OCAMLOPT" != "xno"; then
+        choices="unixnat unix"
+    else
+        choices="unixbyt unix"
+    fi
+    for f in $choices; do
+        if test -f "$OCAMLLIB/lib$f.a"; then
+            CAMLUNIX=$f
+            break
+        fi
+    done
+    if test "x$CAMLUNIX" != "x"; then
+        AC_MSG_RESULT([$CAMLUNIX])
+    else
+        AC_MSG_ERROR([could not find or link to -lunix*])
+    fi
+    AC_SUBST([CAMLUNIX])
 fi
 
 dnl Define HIVEX_OPEN_UNSAFE_FLAG based on test above.