From 1af2c25f9a41c1d6a35621614f748d0563259f40 Mon Sep 17 00:00:00 2001
From: Jimmy Bogard <jimmy.bogard@gmail.com>
Date: Sat, 21 Feb 2026 16:47:39 -0600
Subject: [PATCH] Fixing bug around order of open generic registration

---
 src/AutoMapper/ProfileMap.cs                  |  2 +-
 .../Bug/OpenGenericInheritanceOrder.cs        | 40 +++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 src/UnitTests/Bug/OpenGenericInheritanceOrder.cs

diff --git a/src/AutoMapper/ProfileMap.cs b/src/AutoMapper/ProfileMap.cs
index a4ed1c3bdd..d76d4c2f15 100644
--- a/src/AutoMapper/ProfileMap.cs
+++ b/src/AutoMapper/ProfileMap.cs
@@ -171,7 +171,7 @@ public void Configure(IGlobalConfiguration configuration)
     }
     private void Configure(TypeMapConfiguration typeMapConfiguration, IGlobalConfiguration configuration)
     {
-        var typeMap = typeMapConfiguration.TypeMap;
+        var typeMap = configuration.FindTypeMapFor(typeMapConfiguration.Types);
         if (typeMap.IncludeAllDerivedTypes)
         {
             IncludeAllDerived(configuration, typeMap);
diff --git a/src/UnitTests/Bug/OpenGenericInheritanceOrder.cs b/src/UnitTests/Bug/OpenGenericInheritanceOrder.cs
new file mode 100644
index 0000000000..acacba2325
--- /dev/null
+++ b/src/UnitTests/Bug/OpenGenericInheritanceOrder.cs
@@ -0,0 +1,40 @@
+namespace AutoMapper.UnitTests.Bug;
+
+public class OpenGenericInheritanceOrder
+{
+    class FooBar { }
+    class SourceBase<T> { public string Name { get; set; } }
+    class DestinationBase { public string Name { get; set; } }
+    class SourceDerived : SourceBase<FooBar> { }
+    class DestinationDerived : DestinationBase { }
+
+    [Fact]
+    public void Should_work_when_derived_map_declared_before_open_generic_base_map()
+    {
+        var config = new MapperConfiguration(cfg =>
+        {
+            cfg.CreateMap<SourceDerived, DestinationDerived>()
+                .IncludeBase<SourceBase<FooBar>, DestinationBase>();
+            cfg.CreateMap(typeof(SourceBase<>), typeof(DestinationBase));
+        });
+
+        var mapper = config.CreateMapper();
+        var result = mapper.Map<DestinationDerived>(new SourceDerived { Name = "test" });
+        result.Name.ShouldBe("test");
+    }
+
+    [Fact]
+    public void Should_work_when_open_generic_base_map_declared_first()
+    {
+        var config = new MapperConfiguration(cfg =>
+        {
+            cfg.CreateMap(typeof(SourceBase<>), typeof(DestinationBase));
+            cfg.CreateMap<SourceDerived, DestinationDerived>()
+                .IncludeBase<SourceBase<FooBar>, DestinationBase>();
+        });
+
+        var mapper = config.CreateMapper();
+        var result = mapper.Map<DestinationDerived>(new SourceDerived { Name = "test" });
+        result.Name.ShouldBe("test");
+    }
+}