diff --git a/src/Microsoft.OpenApi/Extensions/OpenApiTypeMapper.cs b/src/Microsoft.OpenApi/Extensions/OpenApiTypeMapper.cs
index 712e7f5c7..b85add3ff 100644
--- a/src/Microsoft.OpenApi/Extensions/OpenApiTypeMapper.cs
+++ b/src/Microsoft.OpenApi/Extensions/OpenApiTypeMapper.cs
@@ -100,9 +100,11 @@ public static Type MapOpenApiPrimitiveTypeToSimpleType(this OpenApiSchema schema
                 ("boolean", null, false) => typeof(bool),
                 ("integer", "int32", false) => typeof(int),
                 ("integer", "int64", false) => typeof(long),
+                ("integer", null, false) => typeof(int),
                 ("number", "float", false) => typeof(float),
                 ("number", "double", false) => typeof(double),
                 ("number", "decimal", false) => typeof(decimal),
+                ("number", null, false) => typeof(double),
                 ("string", "byte", false) => typeof(byte),
                 ("string", "date-time", false) => typeof(DateTimeOffset),
                 ("string", "uuid", false) => typeof(Guid),
@@ -113,8 +115,10 @@ public static Type MapOpenApiPrimitiveTypeToSimpleType(this OpenApiSchema schema
                 ("string", "uri", false) => typeof(Uri),
                 ("integer", "int32", true) => typeof(int?),
                 ("integer", "int64", true) => typeof(long?),
+                ("integer", null, true) => typeof(int?),
                 ("number", "float", true) => typeof(float?),
                 ("number", "double", true) => typeof(double?),
+                ("number", null, true) => typeof(double?),
                 ("number", "decimal", true) => typeof(decimal?),
                 ("string", "byte", true) => typeof(byte?),
                 ("string", "date-time", true) => typeof(DateTimeOffset?),
diff --git a/test/Microsoft.OpenApi.Tests/Extensions/OpenApiTypeMapperTests.cs b/test/Microsoft.OpenApi.Tests/Extensions/OpenApiTypeMapperTests.cs
index a0fcb133a..ee6d6e658 100644
--- a/test/Microsoft.OpenApi.Tests/Extensions/OpenApiTypeMapperTests.cs
+++ b/test/Microsoft.OpenApi.Tests/Extensions/OpenApiTypeMapperTests.cs
@@ -24,6 +24,8 @@ public class OpenApiTypeMapperTests
         public static IEnumerable<object[]> OpenApiDataTypes => new List<object[]>
         {
             new object[] { new OpenApiSchema { Type = "integer", Format = "int32"}, typeof(int) },
+            new object[] { new OpenApiSchema { Type = "integer", Format = null, Nullable = false}, typeof(int) },
+            new object[] { new OpenApiSchema { Type = "integer", Format = null, Nullable = true}, typeof(int?) },
             new object[] { new OpenApiSchema { Type = "string" }, typeof(string) },
             new object[] { new OpenApiSchema { Type = "number", Format = "double" }, typeof(double) },
             new object[] { new OpenApiSchema { Type = "number", Format = "float", Nullable = true }, typeof(float?) },