diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml
index 3623ef015a..e84ac6ae42 100644
--- a/man/systemd-nspawn.xml
+++ b/man/systemd-nspawn.xml
@@ -527,14 +527,14 @@
       </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>Specifies an environment variable assignment
-        to pass to the init process in the container, in the format
-        <literal>NAME=VALUE</literal>. This may be used to override
-        the default variables or to set additional variables. This
-        parameter may be used more than once.</para></listitem>
+        <listitem><para>Specifies an environment variable to pass to the init process in the container. This
+        may be used to override the default variables or to set additional variables. It 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></listitem>
       </varlistentry>
 
       <varlistentry>
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index cf89b27dfa..3d7e20e72e 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -338,7 +338,7 @@ static int help(void) {
                "  -a --as-pid2              Maintain a stub init as PID1, invoke binary as PID2\n"
                "  -b --boot                 Boot up full system (i.e. invoke init)\n"
                "     --chdir=PATH           Set working directory in the container\n"
-               "  -E --setenv=NAME=VALUE    Pass an environment variable to PID 1\n"
+               "  -E --setenv=NAME[=VALUE]  Pass an environment variable to PID 1\n"
                "  -u --user=USER            Run the command under specified user or UID\n"
                "     --kill-signal=SIGNAL   Select signal to use for shutting down PID 1\n"
                "     --notify-ready=BOOLEAN Receive notifications from the child init process\n\n"
@@ -1121,17 +1121,13 @@ static int parse_argv(int argc, char *argv[]) {
                         arg_settings_mask |= SETTING_CUSTOM_MOUNTS;
                         break;
 
-                case 'E': {
-                        if (!env_assignment_is_valid(optarg))
-                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
-                                                       "Environment variable assignment '%s' is not valid.", optarg);
-                        r = strv_env_replace_strdup(&arg_setenv, optarg);
+                case 'E':
+                        r = strv_env_replace_strdup_passthrough(&arg_setenv, optarg);
                         if (r < 0)
-                                return r;
+                                return log_error_errno(r, "Cannot assign environment variable %s: %m", optarg);
 
                         arg_settings_mask |= SETTING_ENVIRONMENT;
                         break;
-                }
 
                 case 'q':
                         arg_quiet = true;