diff --git a/build.gradle.kts b/build.gradle.kts
index 8eb1bc8..5363f5c 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -9,7 +9,7 @@ plugins {
 }
 
 group = "io.github.rtmigo"
-version = "0.3.1-SNAPSHOT" //
+version = "0.4.0" // -SNAPSHOT
 
 repositories {
     mavenCentral()
diff --git a/src/main/kotlin/Build.kt b/src/main/kotlin/Build.kt
index f78d114..8093eb0 100644
--- a/src/main/kotlin/Build.kt
+++ b/src/main/kotlin/Build.kt
@@ -1,5 +1,5 @@
 // DO NOT EDIT. Generated by Gradle task "generateBuildKt"
 object Build { 
-    const val version = "0.3.0"
+    const val version = "0.4.0"
     const val date = "2022-10-21"
 }    
\ No newline at end of file
diff --git a/src/main/kotlin/Main.kt b/src/main/kotlin/Main.kt
index 70ab487..50eef91 100644
--- a/src/main/kotlin/Main.kt
+++ b/src/main/kotlin/Main.kt
@@ -4,13 +4,13 @@
  **/
 
 import com.github.ajalt.clikt.core.*
-import com.github.ajalt.clikt.parameters.arguments.argument
 import com.github.ajalt.clikt.parameters.options.*
 import kotlinx.coroutines.runBlocking
 import maven.*
 import stages.build.*
 import stages.sign.*
 import stages.upload.*
+import tools.rethrowingState
 import java.nio.file.*
 import kotlin.io.path.absolute
 
@@ -24,7 +24,7 @@ class Cli : NoOpCliktCommand(
     init {
         versionOption(Build.version) {
             "$commandName $it (${Build.date})\n" +
-                "MIT (c) Artsiom iG <ortemeo@gmail.com>\n" +
+                "ISC (c) Artsiom iG <ortemeo@gmail.com>\n" +
                 "http://github.com/rtmigo/mavence"
         }
     }
@@ -41,6 +41,20 @@ private suspend fun gaa(): GroupArtifact {
 
 data class CliConfig(val trace: Boolean)
 
+open class CheckCentral : CliktCommand(
+    help = "Check that environment is set for publishing to Maven Central") {
+    override fun run() = catchingCommand(this) {
+        fun checkVar(k: String) = rethrowingState(
+            { "Environment variable $k is not set." },
+            { check(System.getenv(k).isNotBlank()) })
+        checkVar(EnvVarNames.MAVEN_GPG_KEY)
+        checkVar(EnvVarNames.MAVEN_GPG_PASSWORD)
+        checkVar(EnvVarNames.SONATYPE_USERNAME)
+        checkVar(EnvVarNames.SONATYPE_PASSWORD)
+        System.err.println("At first glance, everything is OK.")
+    }
+}
+
 open class Local(help: String = "Build, publish to $m2str") : CliktCommand(help = help) {
     override fun run() = catchingCommand(this) {
         cmdLocal(gaa(), isFinal = true)
@@ -48,17 +62,26 @@ open class Local(help: String = "Build, publish to $m2str") : CliktCommand(help
     }
 }
 
+object EnvVarNames {
+    const val MAVEN_GPG_KEY = "MAVEN_GPG_KEY"
+    const val MAVEN_GPG_PASSWORD = "MAVEN_GPG_PASSWORD"
+    const val SONATYPE_USERNAME = "SONATYPE_USERNAME"
+    const val SONATYPE_PASSWORD = "SONATYPE_PASSWORD"
+}
+
+
+
 open class Stage(help: String = "Build, sign, publish to OSSRH Staging") :
     Local(help = help) {
-    val gpgKey by option("--gpg-key", envvar = "MAVEN_GPG_KEY").required()
-    val gpgPwd by option("--gpg-password", envvar = "MAVEN_GPG_PASSWORD").required()
+    val gpgKey by option("--gpg-key", envvar = EnvVarNames.MAVEN_GPG_KEY).required()
+    val gpgPwd by option("--gpg-password", envvar = EnvVarNames.MAVEN_GPG_PASSWORD).required()
 
     protected val sonatypeUser by option(
         "--sonatype-username",
-        envvar = "SONATYPE_USERNAME").required()
+        envvar = EnvVarNames.SONATYPE_USERNAME).required()
     protected val sonatypePassword by option(
         "--sonatype-password",
-        envvar = "SONATYPE_PASSWORD").required()
+        envvar = EnvVarNames.SONATYPE_PASSWORD).required()
 
     override fun run() = catchingCommand(this) {
         cmdSign(
@@ -102,13 +125,13 @@ fun catchingCommand(cmd: CliktCommand, block: suspend () -> Unit) {
             e.printStackTrace()
         else
             System.err.println("ERROR: $e")
-            System.err.println("Run with --trace to see full stack trace.")
+        System.err.println("Run with --trace to see full stack trace.")
     }
 
 }
 
 fun main(args: Array<String>) {
     Cli()
-        .subcommands(Local(), Stage(), Central())
+        .subcommands(Local(), Stage(), Central(), CheckCentral())
         .main(args)
 }
\ No newline at end of file