diff --git a/pkl-core/src/main/java/org/pkl/core/runtime/VmClass.java b/pkl-core/src/main/java/org/pkl/core/runtime/VmClass.java
index 68614aa86..1cbc68c6c 100644
--- a/pkl-core/src/main/java/org/pkl/core/runtime/VmClass.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/VmClass.java
@@ -497,6 +497,7 @@ public EconomicMap<Object, ObjectMember> getTypedToDynamicMembers() {
       if (__typedToDynamicMembers == null) {
         __typedToDynamicMembers =
             createDelegatingMembers(
+                false,
                 (member) ->
                     new UntypedObjectMemberNode(
                         null, new FrameDescriptor(), member, new DelegateToExtraStorageObjNode()));
@@ -512,6 +513,7 @@ public EconomicMap<Object, ObjectMember> getDynamicToTypedMembers() {
       if (__dynamicToTypedMembers == null) {
         __dynamicToTypedMembers =
             createDelegatingMembers(
+                true,
                 (member) ->
                     TypeCheckedPropertyNodeGen.create(
                         null,
@@ -530,6 +532,7 @@ public EconomicMap<Object, ObjectMember> getMapToTypedMembers() {
       if (__mapToTypedMembers == null) {
         __mapToTypedMembers =
             createDelegatingMembers(
+                true,
                 (member) ->
                     TypeCheckedPropertyNodeGen.create(
                         null,
@@ -542,7 +545,7 @@ public EconomicMap<Object, ObjectMember> getMapToTypedMembers() {
   }
 
   private EconomicMap<Object, ObjectMember> createDelegatingMembers(
-      Function<ObjectMember, MemberNode> memberNodeFactory) {
+      boolean isConversionToTyped, Function<ObjectMember, MemberNode> memberNodeFactory) {
     var result = EconomicMaps.<Object, ObjectMember>create();
     for (var cursor = getAllProperties().getEntries(); cursor.advance(); ) {
       var property = cursor.getValue();
@@ -550,6 +553,10 @@ private EconomicMap<Object, ObjectMember> createDelegatingMembers(
       // Dynamic/Map->Typed conversion: Overall it seems more useful for the typed object
       // to inherit its prototype's value for the hidden property (e.g., Module.output).
       if (property.isHidden()) continue;
+      // Dynamic/Map->Typed conversion: a `fixed` or `const` property's value is fixed by its
+      // declaration, so it must not be overridden by whatever value happens to be in the source
+      // Dynamic/Map.
+      if (isConversionToTyped && property.isConstOrFixed()) continue;
 
       var name = cursor.getKey();
       var member =
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input/api/dynamic.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input/api/dynamic.pkl
index 097dca131..2ab0e22cd 100644
--- a/pkl-core/src/test/files/LanguageSnippetTests/input/api/dynamic.pkl
+++ b/pkl-core/src/test/files/LanguageSnippetTests/input/api/dynamic.pkl
@@ -57,6 +57,8 @@ examples {
     module.catch(() -> new Dynamic { name = "Pigeon" }.toTyped(Person).age)
     module.catch(() -> obj.toTyped(Pair)) // Pair is not a Typed
     module.catch(() -> obj.toTyped(ValueRenderer)) // ValueRenderer is abstract
+    (new Dynamic { name = "Pigeon"; id = 99 }).toTyped(FixedPerson)
+    (new Dynamic { name = "Pigeon"; id = 99 }).toTyped(ConstPerson)
   }
 }
 
@@ -89,3 +91,13 @@ local class Person {
   name: String = "Default"
   age: UInt
 }
+
+local class FixedPerson {
+  name: String = "Default"
+  fixed id: Int = 1
+}
+
+local class ConstPerson {
+  name: String = "Default"
+  const id: Int = 1
+}
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input/api/map.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input/api/map.pkl
index 4a178cb1a..bc375fe14 100644
--- a/pkl-core/src/test/files/LanguageSnippetTests/input/api/map.pkl
+++ b/pkl-core/src/test/files/LanguageSnippetTests/input/api/map.pkl
@@ -137,8 +137,12 @@ examples {
     module.catch(() -> Map("name", "Pigeon").toTyped(Person).age)
     module.catch(() -> Map().toTyped(Int))
     module.catch(() -> Map().toTyped(Abstract))
+    Map("name", "Pigeon", "id", 99).toTyped(FixedPerson)
+    Map("name", "Pigeon", "id", 99).toTyped(ConstPerson)
   }
 }
 
 local class Person { name: String = "Default"; age: Int }
 local abstract class Abstract
+local class FixedPerson { name: String = "Default"; fixed id: Int = 1 }
+local class ConstPerson { name: String = "Default"; const id: Int = 1 }
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/api/dynamic.pcf b/pkl-core/src/test/files/LanguageSnippetTests/output/api/dynamic.pcf
index adc537afb..6e4627be4 100644
--- a/pkl-core/src/test/files/LanguageSnippetTests/output/api/dynamic.pcf
+++ b/pkl-core/src/test/files/LanguageSnippetTests/output/api/dynamic.pcf
@@ -57,5 +57,13 @@ examples {
     "Tried to read property `age` but its value is undefined."
     "Class `Pair` is not a subtype of `Typed`."
     "Cannot instantiate abstract class `ValueRenderer`."
+    new {
+      name = "Pigeon"
+      id = 1
+    }
+    new {
+      name = "Pigeon"
+      id = 1
+    }
   }
 }
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/api/map.pcf b/pkl-core/src/test/files/LanguageSnippetTests/output/api/map.pcf
index 785937863..4fd901c1b 100644
--- a/pkl-core/src/test/files/LanguageSnippetTests/output/api/map.pcf
+++ b/pkl-core/src/test/files/LanguageSnippetTests/output/api/map.pcf
@@ -129,5 +129,13 @@ examples {
     "Tried to read property `age` but its value is undefined."
     "Class `Int` is not a subtype of `Typed`."
     "Cannot instantiate abstract class `map#Abstract`."
+    new {
+      name = "Pigeon"
+      id = 1
+    }
+    new {
+      name = "Pigeon"
+      id = 1
+    }
   }
 }