diff --git a/partiql-ast/api/partiql-ast.api b/partiql-ast/api/partiql-ast.api
index d4a017592..e31c4c6b0 100644
--- a/partiql-ast/api/partiql-ast.api
+++ b/partiql-ast/api/partiql-ast.api
@@ -2816,11 +2816,11 @@ public class org/partiql/ast/expr/TrimSpec : org/partiql/ast/AstEnum {
 public class org/partiql/ast/expr/TruthValue : org/partiql/ast/AstEnum {
 	public static final field FALSE I
 	public static final field TRUE I
-	public static final field UNK I
+	public static final field UNKNOWN I
 	public fun <init> (I)V
 	public static fun FALSE ()Lorg/partiql/ast/expr/TruthValue;
 	public static fun TRUE ()Lorg/partiql/ast/expr/TruthValue;
-	public static fun UNK ()Lorg/partiql/ast/expr/TruthValue;
+	public static fun UNKNOWN ()Lorg/partiql/ast/expr/TruthValue;
 	public fun accept (Lorg/partiql/ast/AstVisitor;Ljava/lang/Object;)Ljava/lang/Object;
 	protected fun canEqual (Ljava/lang/Object;)Z
 	public fun code ()I
diff --git a/partiql-ast/src/main/java/org/partiql/ast/expr/TruthValue.java b/partiql-ast/src/main/java/org/partiql/ast/expr/TruthValue.java
index 167f7457d..003cacf66 100644
--- a/partiql-ast/src/main/java/org/partiql/ast/expr/TruthValue.java
+++ b/partiql-ast/src/main/java/org/partiql/ast/expr/TruthValue.java
@@ -15,7 +15,7 @@
 public class TruthValue extends AstEnum {
     public static final int TRUE = 0;
     public static final int FALSE = 1;
-    public static final int UNK = 2;
+    public static final int UNKNOWN = 2;
 
     private final int code;
 
@@ -31,8 +31,8 @@ public static TruthValue FALSE() {
         return new TruthValue(FALSE);
     }
     
-    public static TruthValue UNK() {
-        return new TruthValue(UNK);
+    public static TruthValue UNKNOWN() {
+        return new TruthValue(UNKNOWN);
     }
 
     @Override
@@ -46,7 +46,7 @@ public String name() {
         switch (code) {
             case TRUE: return "TRUE";
             case FALSE: return "FALSE";
-            case UNK: return "UNK";
+            case UNKNOWN: return "UNK";
             default: throw new IllegalStateException("Invalid TruthValue code: " + code);
         }
     }
@@ -56,7 +56,7 @@ public static TruthValue parse(@NotNull String value) {
         switch (value) {
             case "TRUE": return TruthValue.TRUE();
             case "FALSE": return TruthValue.FALSE();
-            case "UNK": return TruthValue.UNK();
+            case "UNK": return TruthValue.UNKNOWN();
             default: throw new IllegalArgumentException("No enum constant TruthValue." + value);
         }
     }
diff --git a/partiql-ast/src/main/java/org/partiql/ast/sql/SqlDialect.kt b/partiql-ast/src/main/java/org/partiql/ast/sql/SqlDialect.kt
index e916bb953..759d6c9f5 100644
--- a/partiql-ast/src/main/java/org/partiql/ast/sql/SqlDialect.kt
+++ b/partiql-ast/src/main/java/org/partiql/ast/sql/SqlDialect.kt
@@ -442,7 +442,7 @@ public abstract class SqlDialect : AstVisitor<SqlBlock, SqlBlock>() {
         t = t concat when (node.truthValue.code()) {
             TruthValue.TRUE -> "TRUE"
             TruthValue.FALSE -> "FALSE"
-            TruthValue.UNK -> "UNKNOWN"
+            TruthValue.UNKNOWN -> "UNKNOWN"
             else -> throw UnsupportedOperationException("Cannot print $node")
         }
         return t
diff --git a/partiql-ast/src/test/kotlin/org/partiql/ast/sql/SqlDialectTest.kt b/partiql-ast/src/test/kotlin/org/partiql/ast/sql/SqlDialectTest.kt
index df7270383..9a2123e31 100644
--- a/partiql-ast/src/test/kotlin/org/partiql/ast/sql/SqlDialectTest.kt
+++ b/partiql-ast/src/test/kotlin/org/partiql/ast/sql/SqlDialectTest.kt
@@ -1043,7 +1043,7 @@ class SqlDialectTest {
                 exprBoolTest(
                     value = v("x"),
                     not = false,
-                    truthValue = TruthValue.UNK()
+                    truthValue = TruthValue.UNKNOWN()
                 )
             ),
             expect(
@@ -1051,7 +1051,7 @@ class SqlDialectTest {
                 exprBoolTest(
                     value = v("x"),
                     not = true,
-                    truthValue = TruthValue.UNK()
+                    truthValue = TruthValue.UNKNOWN()
                 )
             ),
             // IS [NOT] NULL
diff --git a/partiql-parser/src/main/kotlin/org/partiql/parser/internal/PartiQLParserDefault.kt b/partiql-parser/src/main/kotlin/org/partiql/parser/internal/PartiQLParserDefault.kt
index 653e9ad10..330bd410e 100644
--- a/partiql-parser/src/main/kotlin/org/partiql/parser/internal/PartiQLParserDefault.kt
+++ b/partiql-parser/src/main/kotlin/org/partiql/parser/internal/PartiQLParserDefault.kt
@@ -1408,7 +1408,7 @@ internal class PartiQLParserDefault : PartiQLParser {
             when (ctx.truthValue.type) {
                 GeneratedParser.TRUE -> exprBoolTest(expr, not, TruthValue.TRUE())
                 GeneratedParser.FALSE -> exprBoolTest(expr, not, TruthValue.FALSE())
-                GeneratedParser.UNKNOWN -> exprBoolTest(expr, not, TruthValue.UNK())
+                GeneratedParser.UNKNOWN -> exprBoolTest(expr, not, TruthValue.UNKNOWN())
                 else -> throw error(ctx, "Unexpected value for boolean test IS [NOT] TRUE|FALSE|UNKNOWN")
             }
         }
diff --git a/partiql-planner/src/main/kotlin/org/partiql/planner/internal/transforms/RexConverter.kt b/partiql-planner/src/main/kotlin/org/partiql/planner/internal/transforms/RexConverter.kt
index 7f90b039a..04a87d147 100644
--- a/partiql-planner/src/main/kotlin/org/partiql/planner/internal/transforms/RexConverter.kt
+++ b/partiql-planner/src/main/kotlin/org/partiql/planner/internal/transforms/RexConverter.kt
@@ -402,7 +402,7 @@ internal object RexConverter {
             var call = when (node.truthValue.code()) {
                 TruthValue.TRUE -> call("is_true", value)
                 TruthValue.FALSE -> call("is_false", value)
-                TruthValue.UNK -> call("is_unknown", value)
+                TruthValue.UNKNOWN -> call("is_unknown", value)
                 else -> error("Unexpected TruthValue: ${node.truthValue}")
             }
             // See SQL99 6.30 pg 216 Rule 2 for equivalence