diff --git a/pkgs/development/compilers/dotnet/fix-clang19-build.patch b/pkgs/development/compilers/dotnet/fix-clang19-build.patch
new file mode 100644
index 000000000000..40964acb24dd
--- /dev/null
+++ b/pkgs/development/compilers/dotnet/fix-clang19-build.patch
@@ -0,0 +1,48 @@
+From 36354a7aca58753893148d62a889ca9e27381ac0 Mon Sep 17 00:00:00 2001
+From: David McFarland <corngood@gmail.com>
+Date: Thu, 2 Jan 2025 15:30:16 -0400
+Subject: [PATCH] fix clang19 build
+
+---
+ src/runtime/src/coreclr/vm/comreflectioncache.hpp | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/src/runtime/src/coreclr/vm/comreflectioncache.hpp b/src/runtime/src/coreclr/vm/comreflectioncache.hpp
+index 08d173e616..12db55251d 100644
+--- a/src/runtime/src/coreclr/vm/comreflectioncache.hpp
++++ b/src/runtime/src/coreclr/vm/comreflectioncache.hpp
+@@ -26,6 +26,7 @@ public:
+ 
+     void Init();
+ 
++#ifndef DACCESS_COMPILE
+     BOOL GetFromCache(Element *pElement, CacheType& rv)
+     {
+         CONTRACTL
+@@ -102,6 +103,7 @@ public:
+         AdjustStamp(TRUE);
+         this->LeaveWrite();
+     }
++#endif // !DACCESS_COMPILE
+ 
+ private:
+     // Lock must have been taken before calling this.
+@@ -141,6 +143,7 @@ private:
+         return CacheSize;
+     }
+ 
++#ifndef DACCESS_COMPILE
+     void AdjustStamp(BOOL hasWriterLock)
+     {
+         CONTRACTL
+@@ -170,6 +173,7 @@ private:
+         if (!hasWriterLock)
+             this->LeaveWrite();
+     }
++#endif // !DACCESS_COMPILE
+ 
+     void UpdateHashTable(SIZE_T hash, int slot)
+     {
+-- 
+2.47.0
+
diff --git a/pkgs/development/compilers/dotnet/vmr.nix b/pkgs/development/compilers/dotnet/vmr.nix
index 45c10ebd3b39..1e71d0bd6509 100644
--- a/pkgs/development/compilers/dotnet/vmr.nix
+++ b/pkgs/development/compilers/dotnet/vmr.nix
@@ -148,6 +148,7 @@ stdenv.mkDerivation rec {
     ]
     ++ lib.optionals (lib.versionOlder version "9") [
       ./fix-aspnetcore-portable-build.patch
+      ./fix-clang19-build.patch
     ];
 
   postPatch =