diff --git a/modules/lang/csharp/packages.el b/modules/lang/csharp/packages.el
index 4db62056d..9731635b9 100644
--- a/modules/lang/csharp/packages.el
+++ b/modules/lang/csharp/packages.el
@@ -4,6 +4,8 @@
 (package! csharp-mode :pin "856ecbc0a78ae3bdc2db2ae4d16be43e2d9d9c5e")
 (package! csproj-mode :pin "a7f0f4610c976a28c41b9b8299892f88b5d0336c")
 (package! sln-mode :pin "0f91d1b957c7d2a7bab9278ec57b54d57f1dbd9c")
+;; sln-mode depends on font-lock-ext
+(package! font-lock-ext :pin "b6c82e8ac7996d96494a54454015a98ceb883feb")
 (when (modulep! +unity)
   (package! shader-mode :pin "d7dc8d0d6fe8914e8b6d5cf2081ad61e6952359c"))
 (when (modulep! +dotnet)