diff --git a/checker/src/test/resources/optionalErrors.baseline b/checker/src/test/resources/optionalErrors.baseline
index 380a690..f143b26 100644
--- a/checker/src/test/resources/optionalErrors.baseline
+++ b/checker/src/test/resources/optionalErrors.baseline
@@ -1,18 +1,18 @@
 Source: {?'key': 'hi'}
 =====>
-ERROR: test_location:1:10: expected type 'optional(string)' but found 'string'
+ERROR: test_location:1:10: expected type 'optional_type(string)' but found 'string'
  | {?'key': 'hi'}
  | .........^
 
 Source: [?'value']
 =====>
-ERROR: test_location:1:3: expected type 'optional(string)' but found 'string'
-  | [?'value']
-  | ..^
+ERROR: test_location:1:3: expected type 'optional_type(string)' but found 'string'
+ | [?'value']
+ | ..^
 
 Source: TestAllTypes{?single_int32: 1}
 =====>
-ERROR: test_location:1:29: expected type 'optional(int)' but found 'int'
+ERROR: test_location:1:29: expected type 'optional_type(int)' but found 'int'
  | TestAllTypes{?single_int32: 1}
  | ............................^
 
@@ -23,4 +23,4 @@ declare a {
 =====>
 ERROR: <input>:1:1: unsupported optional field selection
   | a.?b
-  | ^
\ No newline at end of file
+  | ^
diff --git a/checker/src/test/resources/optionals.baseline b/checker/src/test/resources/optionals.baseline
index adca1ac..cc534f5 100644
--- a/checker/src/test/resources/optionals.baseline
+++ b/checker/src/test/resources/optionals.baseline
@@ -6,47 +6,47 @@ declare a {
 _?._(
   a~map(string, string)^a,
   "b"
-)~optional(string)^select_optional_field
+)~optional_type(string)^select_optional_field
 
 Source: x.y
 declare x {
-  value optional(map(string, string))
+  value optional_type(map(string, string))
 }
 =====>
-x~optional(map(string, string))^x.y~optional(string)
+x~optional_type(map(string, string))^x.y~optional_type(string)
 
 Source: {?'nested': x.b}
 declare x {
-  value optional(map(string, string))
+  value optional_type(map(string, string))
 }
 =====>
 {
-  ?"nested"~string:x~optional(map(string, string))^x.b~optional(string)
+  ?"nested"~string:x~optional_type(map(string, string))^x.b~optional_type(string)
 }~map(string, string)
 
 Source: d.dynamic
 declare d {
-  value optional(dyn)
+  value optional_type(dyn)
 }
 =====>
-d~optional(dyn)^d.dynamic~optional(dyn)
+d~optional_type(dyn)^d.dynamic~optional_type(dyn)
 
 Source: has(d.dynamic)
 declare d {
-  value optional(dyn)
+  value optional_type(dyn)
 }
 =====>
-d~optional(dyn)^d.dynamic~test-only~~bool
+d~optional_type(dyn)^d.dynamic~test-only~~bool
 
 Source: has(e.?b.c)
 declare e {
-  value optional(map(string, dyn))
+  value optional_type(map(string, dyn))
 }
 =====>
 _?._(
-  e~optional(map(string, dyn))^e,
+  e~optional_type(map(string, dyn))^e,
   "b"
-)~optional(dyn)^select_optional_field.c~test-only~~bool
+)~optional_type(dyn)^select_optional_field.c~test-only~~bool
 
 Source: {?'key': {'a': 'b'}.?value}
 =====>
@@ -56,7 +56,7 @@ Source: {?'key': {'a': 'b'}.?value}
       "a"~string:"b"~string
     }~map(string, string),
     "value"
-  )~optional(string)^select_optional_field
+  )~optional_type(string)^select_optional_field
 }~map(string, string)
 
 Source: {?'key': {'a': 'b'}.?value}.key
@@ -67,7 +67,7 @@ Source: {?'key': {'a': 'b'}.?value}.key
       "a"~string:"b"~string
     }~map(string, string),
     "value"
-  )~optional(string)^select_optional_field
+  )~optional_type(string)^select_optional_field
 }~map(string, string).key~string
 
 Source: TestAllTypes{?single_int32: {}.?i}
@@ -76,46 +76,46 @@ TestAllTypes{
   ?single_int32:_?._(
     {}~map(dyn, int),
     "i"
-  )~optional(int)^select_optional_field
+  )~optional_type(int)^select_optional_field
 }~dev.cel.testing.testdata.proto3.TestAllTypes^dev.cel.testing.testdata.proto3.TestAllTypes
 
 Source: [?a, ?b, 'world']
 declare a {
-  value optional(string)
+  value optional_type(string)
 }
 declare b {
-  value optional(string)
+  value optional_type(string)
 }
 =====>
 [
-  ?a~optional(string)^a,
-  ?b~optional(string)^b,
+  ?a~optional_type(string)^a,
+  ?b~optional_type(string)^b,
   "world"~string
 ]~list(string)
 
 Source: [?a, ?b, 2]
 declare a {
-  value optional(string)
+  value optional_type(string)
 }
 declare b {
-  value optional(string)
+  value optional_type(string)
 }
 =====>
 [
-  ?a~optional(string)^a,
-  ?b~optional(string)^b,
+  ?a~optional_type(string)^a,
+  ?b~optional_type(string)^b,
   2~int
 ]~list(dyn)
 
 Source: {?'str':a, 2:3}
 declare a {
-  value optional(string)
+  value optional_type(string)
 }
 declare b {
-  value optional(string)
+  value optional_type(string)
 }
 =====>
 {
-  ?"str"~string:a~optional(string)^a,
+  ?"str"~string:a~optional_type(string)^a,
   2~int:3~int
 }~map(dyn, dyn)
diff --git a/common/src/main/java/dev/cel/common/types/OptionalType.java b/common/src/main/java/dev/cel/common/types/OptionalType.java
index f511bb9..d14d4f8 100644
--- a/common/src/main/java/dev/cel/common/types/OptionalType.java
+++ b/common/src/main/java/dev/cel/common/types/OptionalType.java
@@ -26,7 +26,7 @@
 @Immutable
 public abstract class OptionalType extends CelType {
 
-  public static final String NAME = "optional";
+  public static final String NAME = "optional_type";
 
   @Override
   public CelKind kind() {
diff --git a/common/src/test/java/dev/cel/common/types/CelTypesTest.java b/common/src/test/java/dev/cel/common/types/CelTypesTest.java
index 659d2d3..da5c556 100644
--- a/common/src/test/java/dev/cel/common/types/CelTypesTest.java
+++ b/common/src/test/java/dev/cel/common/types/CelTypesTest.java
@@ -90,7 +90,7 @@ public void createOptionalType() {
     Type optionalType = CelTypes.createOptionalType(CelTypes.INT64);
 
     assertThat(optionalType.hasAbstractType()).isTrue();
-    assertThat(optionalType.getAbstractType().getName()).isEqualTo("optional");
+    assertThat(optionalType.getAbstractType().getName()).isEqualTo("optional_type");
     assertThat(optionalType.getAbstractType().getParameterTypesCount()).isEqualTo(1);
     assertThat(optionalType.getAbstractType().getParameterTypes(0)).isEqualTo(CelTypes.INT64);
   }
@@ -146,7 +146,7 @@ private enum FormatTestCases {
         CelTypes.createFunctionType(
             SimpleType.INT, ImmutableList.of(SimpleType.STRING, SimpleType.UINT)),
         "(string, uint) -> int"),
-    OPTIONAL(OptionalType.create(SimpleType.INT), "optional(int)"),
+    OPTIONAL(OptionalType.create(SimpleType.INT), "optional_type(int)"),
     MAP(MapType.create(SimpleType.INT, SimpleType.STRING), "map(int, string)"),
     TYPE(
         TypeType.create(MapType.create(SimpleType.STRING, SimpleType.STRING)),
diff --git a/common/src/test/java/dev/cel/common/types/OptionalTypeTest.java b/common/src/test/java/dev/cel/common/types/OptionalTypeTest.java
index 42de3ec..9af8f4a 100644
--- a/common/src/test/java/dev/cel/common/types/OptionalTypeTest.java
+++ b/common/src/test/java/dev/cel/common/types/OptionalTypeTest.java
@@ -27,7 +27,7 @@ public class OptionalTypeTest {
   public void createOptionalType_success() {
     OptionalType optionalType = OptionalType.create(SimpleType.STRING);
 
-    assertThat(optionalType.name()).isEqualTo("optional");
+    assertThat(optionalType.name()).isEqualTo("optional_type");
     assertThat(optionalType.kind()).isEqualTo(CelKind.OPAQUE);
     assertThat(optionalType.parameters()).containsExactly(SimpleType.STRING);
   }
diff --git a/extensions/src/test/java/dev/cel/extensions/CelOptionalLibraryTest.java b/extensions/src/test/java/dev/cel/extensions/CelOptionalLibraryTest.java
index 5b5fc42..1b367db 100644
--- a/extensions/src/test/java/dev/cel/extensions/CelOptionalLibraryTest.java
+++ b/extensions/src/test/java/dev/cel/extensions/CelOptionalLibraryTest.java
@@ -1018,7 +1018,9 @@ public void optionalMapCreation_valueIsNonOptional_throws() {
     CelValidationException e =
         assertThrows(CelValidationException.class, () -> cel.compile("{?'hi': 'world'}").getAst());
 
-    assertThat(e).hasMessageThat().contains("expected type 'optional(string)' but found 'string'");
+    assertThat(e)
+        .hasMessageThat()
+        .contains("expected type 'optional_type(string)' but found 'string'");
   }
 
   @Test