diff --git a/hibernate-core/src/main/java/org/hibernate/type/CustomType.java b/hibernate-core/src/main/java/org/hibernate/type/CustomType.java
index 9ebeb90a9e..d02a4b2e4f 100644
--- a/hibernate-core/src/main/java/org/hibernate/type/CustomType.java
+++ b/hibernate-core/src/main/java/org/hibernate/type/CustomType.java
@@ -191,22 +191,36 @@ public class CustomType<J>
 
 	@Override
 	public Serializable disassemble(Object value, SharedSessionContractImplementor session, Object owner) {
-		return (Serializable) disassemble( value, session );
+		return disassembleForCache( value );
 	}
 
 	@Override
 	public Serializable disassemble(Object value, SessionFactoryImplementor sessionFactory) throws HibernateException {
-		return (Serializable) disassemble( value, (SharedSessionContractImplementor) null );
+		return disassembleForCache( value );
 	}
 
-	@Override
-	public Object disassemble(Object value, SharedSessionContractImplementor session) {
+	private Serializable disassembleForCache(Object value) {
 		final Serializable disassembled = getUserType().disassemble( (J) value );
 		// Since UserType#disassemble is an optional operation,
 		// we have to handle the fact that it could produce a null value,
 		// in which case we will try to use a converter for disassembling,
 		// or if that doesn't exist, simply use the domain value as is
 		if ( disassembled == null && value != null ) {
+			final BasicValueConverter<J, Object> valueConverter = getUserType().getValueConverter();
+			if ( valueConverter == null ) {
+				return disassembled;
+			}
+			else {
+				return (Serializable) valueConverter.toRelationalValue( (J) value );
+			}
+		}
+		return disassembled;
+	}
+
+	@Override
+	public Object disassemble(Object value, SharedSessionContractImplementor session) {
+		// Use the value converter if available for conversion to the jdbc representation
+		if ( value != null ) {
 			final BasicValueConverter<J, Object> valueConverter = getUserType().getValueConverter();
 			if ( valueConverter == null ) {
 				return value;
@@ -215,7 +229,7 @@ public class CustomType<J>
 				return valueConverter.toRelationalValue( (J) value );
 			}
 		}
-		return disassembled;
+		return value;
 	}
 
 	@Override
diff --git a/hibernate-core/src/test/java/org/hibernate/orm/test/type/contributor/usertype/ContributedUserTypeTest.java b/hibernate-core/src/test/java/org/hibernate/orm/test/type/contributor/usertype/ContributedUserTypeTest.java
index 6e0f6e0614..eacb7134bc 100644
--- a/hibernate-core/src/test/java/org/hibernate/orm/test/type/contributor/usertype/ContributedUserTypeTest.java
+++ b/hibernate-core/src/test/java/org/hibernate/orm/test/type/contributor/usertype/ContributedUserTypeTest.java
@@ -40,7 +40,19 @@ public class ContributedUserTypeTest {
 		Assertions.assertTrue( type instanceof CustomType, "Type was initialized too early i.e. before type-contributors were run" );
 	}
 
-	@Entity
+	@Test
+	@JiraKey( "HHH-17100" )
+	public void testParameter(SessionFactoryScope scope) {
+		scope.inSession(
+				session -> {
+					session.createSelectionQuery( "from StringWrapperTestEntity e where e.stringWrapper = :p" )
+							.setParameter( "p", new StringWrapper( "abc" ) )
+							.getResultList();
+				}
+		);
+	}
+
+	@Entity(name = "StringWrapperTestEntity")
 	public static class StringWrapperTestEntity implements Serializable {
 		@Id
 		private Integer id;
diff --git a/hibernate-core/src/test/java/org/hibernate/orm/test/type/contributor/usertype/StringWrapperUserType.java b/hibernate-core/src/test/java/org/hibernate/orm/test/type/contributor/usertype/StringWrapperUserType.java
index 957dfa30ae..772e726853 100644
--- a/hibernate-core/src/test/java/org/hibernate/orm/test/type/contributor/usertype/StringWrapperUserType.java
+++ b/hibernate-core/src/test/java/org/hibernate/orm/test/type/contributor/usertype/StringWrapperUserType.java
@@ -96,13 +96,13 @@ public class StringWrapperUserType implements UserType<StringWrapper> {
     @Override
     public Serializable disassemble(StringWrapper value)
 			throws HibernateException {
-        return deepCopy( value );
+        return value == null ? null : value.getValue().getBytes();
     }
 
     @Override
     public StringWrapper assemble(Serializable cached, Object owner)
 			throws HibernateException {
-        return deepCopy( (StringWrapper) cached );
+        return new StringWrapper( new String( (byte[]) cached ) );
     }
 
     @Override