diff --git a/modules/core/src/main/java/org/apache/ignite/internal/managers/communication/UnknownMessageException.java b/modules/commons/src/main/java/org/apache/ignite/internal/managers/communication/UnknownMessageException.java
similarity index 100%
rename from modules/core/src/main/java/org/apache/ignite/internal/managers/communication/UnknownMessageException.java
rename to modules/commons/src/main/java/org/apache/ignite/internal/managers/communication/UnknownMessageException.java
diff --git a/modules/core/src/main/java/org/apache/ignite/plugin/extensions/communication/Message.java b/modules/commons/src/main/java/org/apache/ignite/plugin/extensions/communication/Message.java
similarity index 100%
rename from modules/core/src/main/java/org/apache/ignite/plugin/extensions/communication/Message.java
rename to modules/commons/src/main/java/org/apache/ignite/plugin/extensions/communication/Message.java
diff --git a/modules/core/src/test/java/org/apache/ignite/internal/codegen/MessageProcessorTest.java b/modules/core/src/test/java/org/apache/ignite/internal/codegen/MessageProcessorTest.java
index e1e2e38dbbf5c..bc68a55458ff0 100644
--- a/modules/core/src/test/java/org/apache/ignite/internal/codegen/MessageProcessorTest.java
+++ b/modules/core/src/test/java/org/apache/ignite/internal/codegen/MessageProcessorTest.java
@@ -25,11 +25,13 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import javax.annotation.processing.Processor;
 import javax.tools.JavaFileObject;
 import com.google.testing.compile.Compilation;
 import com.google.testing.compile.Compiler;
 import com.google.testing.compile.JavaFileObjects;
+import org.apache.ignite.Ignite;
 import org.apache.ignite.cache.QueryIndex;
 import org.apache.ignite.cache.QueryIndexType;
 import org.apache.ignite.internal.MessageProcessor;
@@ -38,7 +40,6 @@
 import org.apache.ignite.internal.util.CommonUtils;
 import org.apache.ignite.internal.util.typedef.F;
 import org.apache.ignite.lang.IgniteUuid;
-import org.apache.ignite.plugin.extensions.communication.Message;
 import org.apache.ignite.plugin.extensions.communication.mappers.DefaultEnumMapper;
 import org.apache.ignite.transactions.TransactionIsolation;
 import org.junit.Test;
@@ -363,11 +364,17 @@ static Compilation compile(Processor proc, String... srcFiles) {
         for (String srcFile: srcFiles)
             input.add(javaFile(srcFile));
 
-        File igniteCoreJar = jarForClass(Message.class);
+        File igniteCoreJar = jarForClass(Ignite.class);
         File igniteCodegenJar = jarForClass(Order.class);
         File igniteBinaryApiJar = jarForClass(IgniteUuid.class);
         File igniteCommonsJar = jarForClass(CommonUtils.class);
 
+        // Actually can throw 'duplicate element'. But this would mean the same.
+        assertTrue(
+            "Some classpath locations became the same. A required classpath might be lost.",
+            Set.of(igniteCoreJar, igniteCodegenJar, igniteBinaryApiJar, igniteCommonsJar).size() == 4
+        );
+
         return Compiler.javac()
             .withClasspath(F.asList(igniteCoreJar, igniteCodegenJar, igniteBinaryApiJar, igniteCommonsJar))
             .withProcessors(proc)