diff --git a/gnu/home/services/ssh.scm b/gnu/home/services/ssh.scm
index f0987aee23..d15f5ee912 100644
--- a/gnu/home/services/ssh.scm
+++ b/gnu/home/services/ssh.scm
@@ -69,17 +69,19 @@ (define (serialize-string field value)
                  " " value "\n"))
 
 (define (address-family? obj)
-  (memv obj (list 'unset AF_INET AF_INET6)))
+  (memv obj (list AF_INET AF_INET6)))
+
+(define-maybe address-family)
 
 (define (serialize-address-family field family)
-  (if (eq? 'unset family)
-      ""
+  (if (maybe-value-set? family)
       (string-append "  " (serialize-field-name field) " "
                      (cond ((= family AF_INET) "inet")
                            ((= family AF_INET6) "inet6")
                            ;; The 'else' branch is unreachable.
                            (else (raise (condition (&error)))))
-                     "\n")))
+                     "\n")
+      ""))
 
 (define (natural-number? obj)
   (and (integer? obj) (exact? obj) (> obj 0)))
@@ -115,7 +117,7 @@ (define-configuration openssh-host
    maybe-string
    "Host name---e.g., @code{\"foo.example.org\"} or @code{\"192.168.1.2\"}.")
   (address-family
-   address-family
+   maybe-address-family
    "Address family to use when connecting to this host: one of
 @code{AF_INET} (for IPv4 only), @code{AF_INET6} (for IPv6 only).
 Additionally, the field can be left unset to allow any address family.")
diff --git a/gnu/services/file-sharing.scm b/gnu/services/file-sharing.scm
index 5df8b0d597..75e99f20b7 100644
--- a/gnu/services/file-sharing.scm
+++ b/gnu/services/file-sharing.scm
@@ -114,10 +114,7 @@ (define-maybe string)
 ;; name-value pair for the JSON builder.
 (set! serialize-maybe-string
   (lambda (field-name val)
-    (serialize-string field-name
-                      (if (eq? val 'unset)
-                          ""
-                          val))))
+    (serialize-string field-name (maybe-value val ""))))
 
 (define (string-list? val)
   (and (list? val)
@@ -180,9 +177,9 @@ (define (serialize-file-object field-name val)
 (define-maybe file-object)
 (set! serialize-maybe-file-object
   (lambda (field-name val)
-    (if (eq? val 'unset)
-        (serialize-string field-name "")
-        (serialize-file-object field-name val))))
+    (if (maybe-value-set? val)
+        (serialize-file-object field-name val)
+        (serialize-string field-name ""))))
 
 (define (file-object-list? val)
   (and (list? val)
diff --git a/gnu/services/getmail.scm b/gnu/services/getmail.scm
index ce124f6b11..0a1c34cfd3 100644
--- a/gnu/services/getmail.scm
+++ b/gnu/services/getmail.scm
@@ -111,10 +111,10 @@ (define-configuration getmail-retriever-configuration
    "The type of mail retriever to use.  Valid values include
 @samp{passwd} and @samp{static}.")
   (server
-   (string 'unset)
+   string
    "Name or IP address of the server to retrieve mail from.")
   (username
-   (string 'unset)
+   string
    "Username to login to the mail server with.")
   (port
    (non-negative-integer #f)
@@ -143,7 +143,7 @@ (define (serialize-getmail-destination-configuration field-name val)
 
 (define-configuration getmail-destination-configuration
   (type
-   (string 'unset)
+   string
    "The type of mail destination.  Valid values include @samp{Maildir},
 @samp{Mboxrd} and @samp{MDA_external}.")
   (path
diff --git a/gnu/services/kerberos.scm b/gnu/services/kerberos.scm
index f845c1bd89..c3c7872734 100644
--- a/gnu/services/kerberos.scm
+++ b/gnu/services/kerberos.scm
@@ -39,6 +39,7 @@ (define-module (gnu services kerberos)
 
 
 
+;; TODO Use %unset-value and the define-maybe infrastructure.
 (define unset-field (list 'unset-field))
 
 (define (predicate/unset pred)
diff --git a/gnu/services/messaging.scm b/gnu/services/messaging.scm
index 00a1c80a14..59cb486778 100644
--- a/gnu/services/messaging.scm
+++ b/gnu/services/messaging.scm
@@ -90,6 +90,11 @@ (define (make-pred arg)
                      ((new-def ...)
                       (map (lambda (def target)
                              (if (eq? 'common (syntax->datum target))
+                                 ;; TODO Use the %unset-value variable, or
+                                 ;; even better just simplify this so that it
+                                 ;; doesn't interfere with
+                                 ;; define-configuration and define-maybe
+                                 ;; internals.
                                  #''unset def))
                            #'(def ...) #'(target ...)))
                      ((new-doc ...)
@@ -200,7 +205,7 @@ (define (serialize-file-object-list field-name val)
 (define-maybe file-object-list)
 
 (define (raw-content? val)
-  (not (eq? val 'unset)))
+  (maybe-value-set? val))
 (define (serialize-raw-content field-name val)
   val)
 (define-maybe raw-content)
@@ -474,12 +479,12 @@ (define-all-configurations prosody-configuration
      global)
 
     (http-max-content-size
-     (maybe-non-negative-integer 'unset)
+     (maybe-non-negative-integer %unset-value)
      "Maximum allowed size of the HTTP body (in bytes)."
      common)
 
     (http-external-url
-     (maybe-string 'unset)
+     (maybe-string %unset-value)
      "Some modules expose their own URL in various ways.  This URL is built
 from the protocol, host and port used.  If Prosody sits behind a proxy, the
 public URL will be @code{http-external-url} instead.  See
@@ -556,7 +561,7 @@ (define-all-configurations prosody-configuration
      int-component)
 
     (mod-muc
-     (maybe-mod-muc-configuration 'unset)
+     (maybe-mod-muc-configuration %unset-value)
      "Multi-user chat (MUC) is Prosody's module for allowing you to create
 hosted chatrooms/conferences for XMPP users.
 
@@ -573,7 +578,7 @@ (define-all-configurations prosody-configuration
      ext-component)
 
     (raw-content
-     (maybe-raw-content 'unset)
+     (maybe-raw-content %unset-value)
      "Raw content that will be added to the configuration file."
      common)))
 
diff --git a/gnu/services/networking.scm b/gnu/services/networking.scm
index 3c6395b6ca..9d85728371 100644
--- a/gnu/services/networking.scm
+++ b/gnu/services/networking.scm
@@ -772,7 +772,7 @@ (define-configuration/no-serialization opendht-configuration
 network.  A specific port value can be provided by appending the @code{:PORT}
 suffix.  By default, it uses the Jami bootstrap nodes, but any host can be
 specified here.  It's also possible to disable bootstrapping by explicitly
-setting this field to the @code{'unset} value.")
+setting this field to @code{%unset-value}.")
   (port
    (maybe-number 4222)
    "The UDP port to bind to.  When left unspecified, an available port is
diff --git a/gnu/services/telephony.scm b/gnu/services/telephony.scm
index 7152f3b38d..3d855221e5 100644
--- a/gnu/services/telephony.scm
+++ b/gnu/services/telephony.scm
@@ -307,7 +307,7 @@ (define (jami-shepherd-services config)
          (dbus (jami-configuration-dbus config))
          (dbus-daemon (file-append dbus "/bin/dbus-daemon"))
          (accounts (jami-configuration-accounts config))
-         (declarative-mode? (not (eq? 'unset accounts))))
+         (declarative-mode? (maybe-value-set? accounts)))
 
     (with-extensions (list guile-packrat ;used by guile-ac-d-bus
                            guile-ac-d-bus
@@ -649,7 +649,7 @@ (define (archive-name->username archive)
                                           account-details)
                            (let ((username (archive-name->username
                                             archive)))
-                             (when (not (eq? 'unset allowed-contacts))
+                             (when (not (eq? '#$%unset-value allowed-contacts))
                                ;; Reject calls from unknown contacts.
                                (set-account-details
                                 '(("DHT.PublicInCalls" . "false")) username)
@@ -659,7 +659,7 @@ (define (archive-name->username archive)
                                ;; Add allowed ones.
                                (for-each (cut add-contact <> username)
                                          allowed-contacts))
-                             (when (not (eq? 'unset moderators))
+                             (when (not (eq? '#$%unset-value moderators))
                                ;; Disable the 'AllModerators' property.
                                (set-all-moderators #f username)
                                ;; Remove all moderators.
diff --git a/tests/services/configuration.scm b/tests/services/configuration.scm
index 649dad26e8..8ed4ed4b66 100644
--- a/tests/services/configuration.scm
+++ b/tests/services/configuration.scm
@@ -169,7 +169,7 @@ (define-configuration config-with-maybe-string/no-serialization
   (not (defined? 'serialize-maybe-string)))
 
 (test-assert "maybe type, no default"
-  (eq? 'unset
+  (eq? %unset-value
        (config-with-maybe-string/no-serialization-name
         (config-with-maybe-string/no-serialization))))