diff --git a/src/channel.c b/src/channel.c
index 38e6392..581c6f6 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -4797,9 +4797,15 @@
 	    {
 		if (!(supported2 & JO2_ENV))
 		    break;
+		if (item->v_type != VAR_DICT)
+		{
+		    EMSG2(_(e_invargval), "env");
+		    return FAIL;
+		}
 		opt->jo_set2 |= JO2_ENV;
 		opt->jo_env = item->vval.v_dict;
-		++item->vval.v_dict->dv_refcount;
+		if (opt->jo_env != NULL)
+		    ++opt->jo_env->dv_refcount;
 	    }
 	    else if (STRCMP(hi->hi_key, "cwd") == 0)
 	    {
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index 59283d2..235312e 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -1720,10 +1720,12 @@
 
   let g:envstr = ''
   if has('win32')
-    call job_start(['cmd', '/c', 'echo %FOO%'], {'callback': {ch,msg->execute(":let g:envstr .= msg")}, 'env':{'FOO': 'bar'}})
+    let cmd = ['cmd', '/c', 'echo %FOO%']
   else
-    call job_start([&shell, &shellcmdflag, 'echo $FOO'], {'callback': {ch,msg->execute(":let g:envstr .= msg")}, 'env':{'FOO': 'bar'}})
+    let cmd = [&shell, &shellcmdflag, 'echo $FOO']
   endif
+  call assert_fails('call job_start(cmd, {"env": 1})', 'E475:')
+  call job_start(cmd, {'callback': {ch,msg -> execute(":let g:envstr .= msg")}, 'env': {'FOO': 'bar'}})
   call WaitFor('"" != g:envstr')
   call assert_equal("bar", g:envstr)
   unlet g:envstr
@@ -1737,11 +1739,12 @@
   let g:envstr = ''
   if has('win32')
     let expect = $TEMP
-    let job = job_start(['cmd', '/c', 'echo %CD%'], {'callback': {ch,msg->execute(":let g:envstr .= msg")}, 'cwd': expect})
+    let cmd = ['cmd', '/c', 'echo %CD%']
   else
     let expect = $HOME
-    let job = job_start(['pwd'], {'callback': {ch,msg->execute(":let g:envstr .= msg")}, 'cwd': expect})
+    let cmd = ['pwd']
   endif
+  let job = job_start(cmd, {'callback': {ch,msg -> execute(":let g:envstr .= msg")}, 'cwd': expect})
   try
     call WaitFor('"" != g:envstr')
     let expect = substitute(expect, '[/\\]$', '', '')
diff --git a/src/version.c b/src/version.c
index 59ca7a8..8264bd9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -763,6 +763,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1671,
+/**/
     1670,
 /**/
     1669,