diff --git a/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/FunctionProvider.kt b/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/FunctionProvider.kt
index a29b267723..2c0e59c1f8 100644
--- a/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/FunctionProvider.kt
+++ b/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/FunctionProvider.kt
@@ -539,7 +539,7 @@ abstract class FunctionProvider {
         val autoIncColumn = table.autoIncColumn
         val nextValExpression = autoIncColumn?.autoIncColumnType?.nextValExpression
         val dataColumnsWithoutAutoInc = autoIncColumn?.let { dataColumns - autoIncColumn } ?: dataColumns
-        val updateColumns = dataColumns.filter { it !in keyColumns }
+        val updateColumns = dataColumns.filter { it !in keyColumns }.ifEmpty { dataColumns }
 
         return with(QueryBuilder(true)) {
             +"MERGE INTO "
diff --git a/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/PostgreSQL.kt b/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/PostgreSQL.kt
index 8946649cb6..63fefcb0fa 100644
--- a/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/PostgreSQL.kt
+++ b/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/PostgreSQL.kt
@@ -249,7 +249,8 @@ internal object PostgreSQLFunctionProvider : FunctionProvider() {
             transaction.throwUnsupportedException("UPSERT requires a unique key or constraint as a conflict target")
         }
 
-        val updateColumns = data.unzip().first.filter { it !in keyColumns }
+        val dataColumns = data.unzip().first
+        val updateColumns = dataColumns.filter { it !in keyColumns }.ifEmpty { dataColumns }
 
         return with(QueryBuilder(true)) {
             appendInsertToUpsertClause(table, data, transaction)
diff --git a/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/SQLiteDialect.kt b/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/SQLiteDialect.kt
index 31410675b2..90d16627cb 100644
--- a/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/SQLiteDialect.kt
+++ b/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/SQLiteDialect.kt
@@ -216,7 +216,8 @@ internal object SQLiteFunctionProvider : FunctionProvider() {
         }
 
         +" DO"
-        val updateColumns = data.unzip().first.filter { it !in keyColumns }
+        val dataColumns = data.unzip().first
+        val updateColumns = dataColumns.filter { it !in keyColumns }.ifEmpty { dataColumns }
         appendUpdateToUpsertClause(table, updateColumns, onUpdate, transaction, isAliasNeeded = false)
 
         where?.let {
diff --git a/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/dml/UpsertTests.kt b/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/dml/UpsertTests.kt
index 554f95a621..82d97c8841 100644
--- a/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/dml/UpsertTests.kt
+++ b/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/dml/UpsertTests.kt
@@ -1,6 +1,7 @@
 package org.jetbrains.exposed.sql.tests.shared.dml
 
 import org.jetbrains.exposed.dao.id.IntIdTable
+import org.jetbrains.exposed.exceptions.ExposedSQLException
 import org.jetbrains.exposed.exceptions.UnsupportedByDialectException
 import org.jetbrains.exposed.sql.*
 import org.jetbrains.exposed.sql.SqlExpressionBuilder.concat
@@ -14,6 +15,7 @@ import org.jetbrains.exposed.sql.tests.shared.expectException
 import org.junit.Test
 import java.util.*
 import kotlin.properties.Delegates
+import kotlin.test.assertNotNull
 
 // Upsert implementation does not support H2 version 1
 // https://youtrack.jetbrains.com/issue/EXPOSED-30/Phase-Out-Support-for-H2-Version-1.x
@@ -86,6 +88,46 @@ class UpsertTests : DatabaseTestsBase() {
         }
     }
 
+    @Test
+    fun testUpsertWithAllColumnsInPK() {
+        val tester = object : Table("tester") {
+            val userId = varchar("user_id", 32)
+            val keyId = varchar("key_id", 32)
+            override val primaryKey = PrimaryKey(userId, keyId)
+        }
+
+        fun upsertOnlyKeyColumns(values: Pair<String, String>) {
+            tester.upsert {
+                it[userId] = values.first
+                it[keyId] = values.second
+            }
+        }
+
+        withTables(tester) { testDb ->
+            excludingH2Version1(testDb) {
+                val primaryKeyValues = Pair("User A", "Key A")
+                if (testDb == TestDB.ORACLE) {
+                    // Oracle explicitly prohibits using key columns in update clause
+                    // throws 'ORA-38104: Columns referenced in the ON Clause cannot be updated'
+                    expectException<ExposedSQLException> {
+                        upsertOnlyKeyColumns(primaryKeyValues)
+                    }
+                } else {
+                    // insert new row
+                    upsertOnlyKeyColumns(primaryKeyValues)
+                    // 'update' existing row to have identical values
+                    upsertOnlyKeyColumns(primaryKeyValues)
+
+                    val result = tester.selectAll().singleOrNull()
+                    assertNotNull(result)
+
+                    val resultValues = Pair(result[tester.userId], result[tester.keyId])
+                    assertEquals(primaryKeyValues, resultValues)
+                }
+            }
+        }
+    }
+
     @Test
     fun testUpsertWithUniqueIndexConflict() {
         withTables(Words) { testDb ->