diff --git a/hoptimator-catalog/src/main/java/com/linkedin/hoptimator/catalog/ScriptImplementor.java b/hoptimator-catalog/src/main/java/com/linkedin/hoptimator/catalog/ScriptImplementor.java
index e9368ef..6a5e6e8 100644
--- a/hoptimator-catalog/src/main/java/com/linkedin/hoptimator/catalog/ScriptImplementor.java
+++ b/hoptimator-catalog/src/main/java/com/linkedin/hoptimator/catalog/ScriptImplementor.java
@@ -170,7 +170,7 @@ public SqlNode visit(SqlCall call) {
    * Implements a CREATE TABLE...WITH... DDL statement.
    *
    * N.B. the following magic:
-   *  - field 'KEY' is treated as a PRIMARY KEY
+   *  - non-nullable field 'KEY' is treated as a PRIMARY KEY
    */
   class ConnectorImplementor implements ScriptImplementor {
     private final String database;
@@ -192,7 +192,8 @@ public void implement(SqlWriter w) {
       (new CompoundIdentifierImplementor(database, name)).implement(w);
       SqlWriter.Frame frame1 = w.startList("(", ")");
       (new RowTypeSpecImplementor(rowType)).implement(w);
-      if (rowType.getField("KEY", true, false) != null) {
+      RelDataTypeField key = rowType.getField("KEY", true, false);
+      if (key != null && key.getType().isNullable() == false) {
         w.sep(",");
         w.literal("PRIMARY KEY (KEY) NOT ENFORCED");
       }