diff --git a/man/machinectl.xml b/man/machinectl.xml
index ad47b6102e3..7ecb8885a25 100644
--- a/man/machinectl.xml
+++ b/man/machinectl.xml
@@ -712,14 +712,16 @@
       </varlistentry>
 
       <varlistentry>
-        <term><option>-E <replaceable>NAME</replaceable>=<replaceable>VALUE</replaceable></option></term>
-        <term><option>--setenv=<replaceable>NAME</replaceable>=<replaceable>VALUE</replaceable></option></term>
+        <term><option>-E <replaceable>NAME</replaceable>[=<replaceable>VALUE</replaceable>]</option></term>
+        <term><option>--setenv=<replaceable>NAME</replaceable>[=<replaceable>VALUE</replaceable>]</option></term>
 
-         <listitem><para>When used with the <command>shell</command> command, sets an environment
-         variable to pass to the executed shell. Takes an environment variable name and value,
-         separated by <literal>=</literal>. This switch may be used multiple times to set multiple
-         environment variables. Note that this switch is not supported for the
-         <command>login</command> command (see below).</para></listitem>
+        <listitem><para>When used with the <command>shell</command> command, sets an environment variable for
+        the executed shell. This option may be used more than once to set multiple variables. When
+        <literal>=</literal> and <replaceable>VALUE</replaceable> are omitted, the value of the variable with
+        the same name in the program environment will be used.</para>
+
+        <para>Note that this option is not supported for the <command>login</command> command.
+        </para></listitem>
       </varlistentry>
 
       <varlistentry>
diff --git a/src/machine/machinectl.c b/src/machine/machinectl.c
index b4c251078ba..3f4ad878972 100644
--- a/src/machine/machinectl.c
+++ b/src/machine/machinectl.c
@@ -2510,7 +2510,7 @@ static int help(int argc, char *argv[], void *userdata) {
                "     --kill-who=WHO           Who to send signal to\n"
                "  -s --signal=SIGNAL          Which signal to send\n"
                "     --uid=USER               Specify user ID to invoke shell as\n"
-               "  -E --setenv=VAR=VALUE       Add an environment variable for shell\n"
+               "  -E --setenv=VAR[=VALUE]     Add an environment variable for shell\n"
                "     --read-only              Create read-only bind mount\n"
                "     --mkdir                  Create directory before bind mounting, if missing\n"
                "  -n --lines=INTEGER          Number of journal entries to show\n"
@@ -2765,13 +2765,9 @@ static int parse_argv(int argc, char *argv[]) {
                         break;
 
                 case 'E':
-                        if (!env_assignment_is_valid(optarg))
-                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
-                                                       "Environment assignment invalid: %s", optarg);
-
-                        r = strv_extend(&arg_setenv, optarg);
+                        r = strv_env_replace_strdup_passthrough(&arg_setenv, optarg);
                         if (r < 0)
-                                return log_oom();
+                                return log_error_errno(r, "Cannot assign environment variable %s: %m", optarg);
                         break;
 
                 case ARG_MAX_ADDRESSES: