diff --git a/jOOQ-codegen/src/main/java/org/jooq/util/JavaGenerator.java b/jOOQ-codegen/src/main/java/org/jooq/util/JavaGenerator.java
index c1540dfa12..d77c465d41 100644
--- a/jOOQ-codegen/src/main/java/org/jooq/util/JavaGenerator.java
+++ b/jOOQ-codegen/src/main/java/org/jooq/util/JavaGenerator.java
@@ -4429,17 +4429,20 @@ public class JavaGenerator extends AbstractGenerator {
 
             // Otherwise, reference the dialect-specific DataType itself.
             else {
-                String typeClass =
-                    "org.jooq.util." +
-                    db.getDialect().getName().toLowerCase() +
-                    "." +
-                    db.getDialect().getName() +
-                    "DataType";
-
-                sb.append(typeClass);
-                sb.append(".");
-
                 try {
+
+                    // [#4173] DEFAULT and SQL99 data types
+                    String typeClass = (db.getDialect().getName() == null)
+                        ? SQLDataType.class.getName()
+                        : "org.jooq.util." +
+                          db.getDialect().getName().toLowerCase() +
+                          "." +
+                          db.getDialect().getName() +
+                          "DataType";
+
+                    sb.append(typeClass);
+                    sb.append(".");
+
                     String type1 = getType(db, schema, t, p, s, u, null);
                     String type2 = getType(db, schema, t, 0, 0, u, null);
                     String typeName = DefaultDataType.normalise(t);
diff --git a/jOOQ/src/main/java/org/jooq/SQLDialect.java b/jOOQ/src/main/java/org/jooq/SQLDialect.java
index 0d1760f596..9c3b74e10b 100644
--- a/jOOQ/src/main/java/org/jooq/SQLDialect.java
+++ b/jOOQ/src/main/java/org/jooq/SQLDialect.java
@@ -66,7 +66,7 @@ public enum SQLDialect {
      *             pseudo-dialect.
      */
     @Deprecated
-    SQL99(null, false),
+    SQL99("", false),
 
     /**
      * The default SQL dialect.
@@ -75,7 +75,7 @@ public enum SQLDialect {
      * not intended to be used with any actual database as it may combined
      * dialect-specific things from various dialects.
      */
-    DEFAULT(null, false),
+    DEFAULT("", false),
 
     // -------------------------------------------------------------------------
     // SQL dialects for free usage