diff --git a/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/SQLExpressionBuilder.kt b/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/SQLExpressionBuilder.kt
index 376b66d9ca..dbc93be5c0 100644
--- a/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/SQLExpressionBuilder.kt
+++ b/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/SQLExpressionBuilder.kt
@@ -148,8 +148,8 @@ interface ISqlExpressionBuilder {
     }
 
     /** Checks if this expression is equals to some [other] expression. */
-    infix fun <T, S1 : T?, S2 : T?> Expression<in S1>.eq(other: Expression<in S2>): Op<Boolean> = when {
-        other.equals(Op.NULL) -> isNull()
+    infix fun <T, S1 : T?, S2 : T?> Expression<in S1>.eq(other: Expression<in S2>): Op<Boolean> = when (other as Expression<*>) {
+        is Op.NULL -> isNull()
         else -> EqOp(this, other)
     }
 
diff --git a/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/DDLTests.kt b/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/DDLTests.kt
index 08876116e8..8a176f4466 100644
--- a/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/DDLTests.kt
+++ b/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/DDLTests.kt
@@ -686,6 +686,19 @@ class DDLTests : DatabaseTestsBase() {
         }
     }
 
+    @Test
+    fun testCheckConstraint03() {
+        object : Table("test") {
+            val testColumn: Column<Int?> = integer("test_column").nullable()
+
+            init {
+                check("test_constraint") {
+                    testColumn.isNotNull() eq Op.TRUE
+                }
+            }
+        }
+    }
+
     internal enum class Foo { Bar, Baz }
 
     class PGEnum<T : Enum<T>>(enumTypeName: String, enumValue: T?) : PGobject() {