diff --git a/src/Microsoft.OpenApi/Models/OpenApiSchema.cs b/src/Microsoft.OpenApi/Models/OpenApiSchema.cs
index 1ffccd272..e0b4ae495 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiSchema.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiSchema.cs
@@ -489,9 +489,8 @@ private void SerializeInternal(IOpenApiWriter writer, OpenApiSpecVersion version
                     AdditionalProperties,
                     callback);
             }
-            // true is the default in earlier versions 3, no need to write it out
-            // boolean value is only supported for version 3 and earlier (version 2 is implemented in the other serialize method, the condition is a failsafe)
-            else if (!AdditionalPropertiesAllowed && version <= OpenApiSpecVersion.OpenApi3_0)
+            // true is the default, no need to write it out
+            else if (!AdditionalPropertiesAllowed)
             {
                 writer.WriteProperty(OpenApiConstants.AdditionalProperties, AdditionalPropertiesAllowed);
             }
diff --git a/test/Microsoft.OpenApi.Tests/Models/OpenApiSchemaTests.cs b/test/Microsoft.OpenApi.Tests/Models/OpenApiSchemaTests.cs
index c20da3127..67a79e35e 100644
--- a/test/Microsoft.OpenApi.Tests/Models/OpenApiSchemaTests.cs
+++ b/test/Microsoft.OpenApi.Tests/Models/OpenApiSchemaTests.cs
@@ -754,8 +754,10 @@ public async Task SerializeAdditionalPropertiesAllowedAsV3PlusDefaultDoesNotEmit
             Assert.True(JsonNode.DeepEquals(JsonNode.Parse(expected), JsonNode.Parse(actual)));
         }
 
-        [Fact]
-        public async Task SerializeAdditionalPropertiesAllowedAsV3FalseEmits()
+        [Theory]
+        [InlineData(OpenApiSpecVersion.OpenApi3_0)]
+        [InlineData(OpenApiSpecVersion.OpenApi3_1)]
+        public async Task SerializeAdditionalPropertiesAllowedAsV3PlusFalseEmits(OpenApiSpecVersion version)
         {
             var expected = @"{ ""additionalProperties"": false }";
             // Given
@@ -765,7 +767,7 @@ public async Task SerializeAdditionalPropertiesAllowedAsV3FalseEmits()
             };
 
             // When
-            var actual = await schema.SerializeAsJsonAsync(OpenApiSpecVersion.OpenApi3_0);
+            var actual = await schema.SerializeAsJsonAsync(version);
 
             // Then
             Assert.True(JsonNode.DeepEquals(JsonNode.Parse(expected), JsonNode.Parse(actual)));