diff --git a/jOOQ-test/src/org/jooq/test/BaseTest.java b/jOOQ-test/src/org/jooq/test/BaseTest.java
index d7729f4f89..99c3ff9af0 100644
--- a/jOOQ-test/src/org/jooq/test/BaseTest.java
+++ b/jOOQ-test/src/org/jooq/test/BaseTest.java
@@ -52,8 +52,6 @@ import org.jooq.ArrayRecord;
 import org.jooq.DAO;
 import org.jooq.DataType;
 import org.jooq.Field;
-import org.jooq.QueryPart;
-import org.jooq.QueryPartInternal;
 import org.jooq.Record;
 import org.jooq.Result;
 import org.jooq.SQLDialect;
@@ -691,10 +689,6 @@ public abstract class BaseTest<
         return delegate.getDialect();
     }
 
-    protected final QueryPartInternal internal(QueryPart q) {
-        return delegate.internal(q);
-    }
-
     protected final void sleep(long millis) {
         try {
             Thread.sleep(millis);
diff --git a/jOOQ-test/src/org/jooq/test/jOOQAbstractTest.java b/jOOQ-test/src/org/jooq/test/jOOQAbstractTest.java
index 72d23a5385..88f04e73fc 100644
--- a/jOOQ-test/src/org/jooq/test/jOOQAbstractTest.java
+++ b/jOOQ-test/src/org/jooq/test/jOOQAbstractTest.java
@@ -62,8 +62,6 @@ import org.jooq.DAO;
 import org.jooq.DataType;
 import org.jooq.ExecuteType;
 import org.jooq.Field;
-import org.jooq.QueryPart;
-import org.jooq.QueryPartInternal;
 import org.jooq.Record;
 import org.jooq.Result;
 import org.jooq.SQLDialect;
@@ -718,10 +716,6 @@ public abstract class jOOQAbstractTest<
         return create().getDialect();
     }
 
-    protected final QueryPartInternal internal(QueryPart q) {
-        return q.internalAPI(QueryPartInternal.class);
-    }
-
     protected String getSchemaSuffix() {
         return "";
     }
diff --git a/jOOQ/src/main/java/org/jooq/Adapter.java b/jOOQ/src/main/java/org/jooq/Adapter.java
index 41ef0b6849..724b4af3ed 100644
--- a/jOOQ/src/main/java/org/jooq/Adapter.java
+++ b/jOOQ/src/main/java/org/jooq/Adapter.java
@@ -41,7 +41,10 @@ package org.jooq;
  * This interface is for JOOQ INTERNAL USE only. Do not reference directly
  *
  * @author Lukas Eder
+ * @deprecated - 2.5.0 [#1639] - This part of the internal API will be removed
+ *             in the near future. Do not reuse.
  */
+@Deprecated
 public interface Adapter {
 
     /**
@@ -60,6 +63,9 @@ public interface Adapter {
      * @return This object wrapped by or cast to an internal type
      * @throws ClassCastException If this object cannot be wrapped by or cast to
      *             the given internal type
+     * @deprecated - 2.5.0 [#1639] - This part of the internal API will be
+     *             removed in the near future. Do not reuse.
      */
+    @Deprecated
     <I> I internalAPI(Class<I> internalType) throws ClassCastException;
 }
diff --git a/jOOQ/src/main/java/org/jooq/Attachable.java b/jOOQ/src/main/java/org/jooq/Attachable.java
index e752b631b8..a6ee90c5f4 100644
--- a/jOOQ/src/main/java/org/jooq/Attachable.java
+++ b/jOOQ/src/main/java/org/jooq/Attachable.java
@@ -56,6 +56,7 @@ import java.sql.Connection;
  *
  * @author Lukas Eder
  */
+@SuppressWarnings("deprecation")
 public interface Attachable extends Adapter, Serializable {
 
     /**
diff --git a/jOOQ/src/main/java/org/jooq/QueryPart.java b/jOOQ/src/main/java/org/jooq/QueryPart.java
index 5ce5c376ed..fe1dafda27 100644
--- a/jOOQ/src/main/java/org/jooq/QueryPart.java
+++ b/jOOQ/src/main/java/org/jooq/QueryPart.java
@@ -39,22 +39,21 @@ package org.jooq;
  * The common base type for all objects that can be used for query composition.
  * <p>
  * All <code>QueryPart</code> implementations can be cast to
- * {@link QueryPartInternal} in order to access the internal API. See also
- * {@link #internalAPI(Class)}
+ * {@link QueryPartInternal} in order to access the internal API.
  * <p>
  * A <code>QueryPart</code> essentially combines the {@link Attachable}
  * interface with SQL code generation and variable binding functionality.
  * <p>
  * Note that with jOOQ 3.0, <code>QueryPart</code> will no longer implement
  * {@link Attachable}.
- * 
+ *
  * @author Lukas Eder
  */
 public interface QueryPart extends Attachable {
 
     /**
      * Attach this object to a new {@link Configuration}
-     * 
+     *
      * @deprecated - 2.5.0 [#1544] - The Attachable type will no longer be part
      *             of the QueryPart hierarchy. Please do not attach any
      *             <code>QueryPart</code> objects anymore, except for
diff --git a/jOOQ/src/main/java/org/jooq/impl/AbstractBindContext.java b/jOOQ/src/main/java/org/jooq/impl/AbstractBindContext.java
index 6d8541aa3c..645483cb19 100644
--- a/jOOQ/src/main/java/org/jooq/impl/AbstractBindContext.java
+++ b/jOOQ/src/main/java/org/jooq/impl/AbstractBindContext.java
@@ -94,7 +94,7 @@ abstract class AbstractBindContext extends AbstractContext<BindContext> implemen
     @Override
     public final BindContext bind(QueryPart part) {
         if (part != null) {
-            QueryPartInternal internal = part.internalAPI(QueryPartInternal.class);
+            QueryPartInternal internal = (QueryPartInternal) part;
 
             // If this is supposed to be a declaration section and the part isn't
             // able to declare anything, then disable declaration temporarily
diff --git a/jOOQ/src/main/java/org/jooq/impl/BatchStore.java b/jOOQ/src/main/java/org/jooq/impl/BatchStore.java
index 8ee846ab57..48a8a9f2db 100644
--- a/jOOQ/src/main/java/org/jooq/impl/BatchStore.java
+++ b/jOOQ/src/main/java/org/jooq/impl/BatchStore.java
@@ -103,7 +103,7 @@ class BatchStore implements Batch {
             work.setExecuteLogging(false);
 
             for (int i = 0; i < records.length; i++) {
-                Configuration previous = records[i].internalAPI(AttachableInternal.class).getConfiguration();
+                Configuration previous = ((AttachableInternal) records[i]).getConfiguration();
 
                 try {
                     records[i].attach(create);
@@ -175,7 +175,7 @@ class BatchStore implements Batch {
             work.setExecuteListeners(Arrays.asList(QueryCollector.class.getName()));
 
             for (int i = 0; i < records.length; i++) {
-                Configuration previous = records[i].internalAPI(AttachableInternal.class).getConfiguration();
+                Configuration previous = ((AttachableInternal) records[i]).getConfiguration();
 
                 try {
                     records[i].attach(create);
diff --git a/jOOQ/src/main/java/org/jooq/impl/DefaultRenderContext.java b/jOOQ/src/main/java/org/jooq/impl/DefaultRenderContext.java
index 1b6a05195f..d3d6f7df42 100644
--- a/jOOQ/src/main/java/org/jooq/impl/DefaultRenderContext.java
+++ b/jOOQ/src/main/java/org/jooq/impl/DefaultRenderContext.java
@@ -284,7 +284,7 @@ class DefaultRenderContext extends AbstractContext<RenderContext> implements Ren
     @Override
     public final RenderContext sql(QueryPart part) {
         if (part != null) {
-            QueryPartInternal internal = part.internalAPI(QueryPartInternal.class);
+            QueryPartInternal internal = (QueryPartInternal) part;
 
             // If this is supposed to be a declaration section and the part isn't
             // able to declare anything, then disable declaration temporarily
diff --git a/jOOQ/src/main/java/org/jooq/impl/InsertImpl.java b/jOOQ/src/main/java/org/jooq/impl/InsertImpl.java
index 349919cd8f..7c147e363d 100644
--- a/jOOQ/src/main/java/org/jooq/impl/InsertImpl.java
+++ b/jOOQ/src/main/java/org/jooq/impl/InsertImpl.java
@@ -116,7 +116,7 @@ class InsertImpl<R extends Record>
 
     @Override
     public final Insert<R> select(Select<?> select) {
-        Configuration configuration = getDelegate().internalAPI(AttachableInternal.class).getConfiguration();
+        Configuration configuration = ((AttachableInternal) getDelegate()).getConfiguration();
         return new InsertSelectQueryImpl<R>(configuration, into, fields, select);
     }