diff --git a/docs/release-notes/rl-0.8.md b/docs/release-notes/rl-0.8.md
index 9f05f60a..22bc0c43 100644
--- a/docs/release-notes/rl-0.8.md
+++ b/docs/release-notes/rl-0.8.md
@@ -228,8 +228,9 @@
   syncing of nvim shell environment with direnv's.
 - Add [blink.cmp] source options and some default-disabled sources.
 - Add [blink.cmp] option to add
-  [friendly-snippets](https://github.com/rafamadriz/friendly-snippets) so
-  blink.cmp can source snippets from it.
+  [friendly-snippets](https://github.com/rafamadriz/friendly-snippets)
+  so blink.cmp can source snippets from it.
+- Fix [blink.cmp] breaking when built-in sources were modified.
 
 [TheColorman](https://github.com/TheColorman):
 
diff --git a/modules/plugins/completion/blink-cmp/blink-cmp.nix b/modules/plugins/completion/blink-cmp/blink-cmp.nix
index 4290e1cb..a2171552 100644
--- a/modules/plugins/completion/blink-cmp/blink-cmp.nix
+++ b/modules/plugins/completion/blink-cmp/blink-cmp.nix
@@ -21,8 +21,9 @@
     freeformType = anything;
     options = {
       module = mkOption {
-        type = str;
-        description = "module of the provider";
+        type = nullOr str;
+        default = null;
+        description = "Provider module.";
       };
     };
   };
@@ -40,7 +41,7 @@ in {
         providers = mkOption {
           type = attrsOf providerType;
           default = {};
-          description = "Settings for completion providers";
+          description = "Settings for completion providers.";
         };
 
         transform_items = mkOption {
diff --git a/modules/plugins/completion/blink-cmp/config.nix b/modules/plugins/completion/blink-cmp/config.nix
index 875a4fd4..9302332e 100644
--- a/modules/plugins/completion/blink-cmp/config.nix
+++ b/modules/plugins/completion/blink-cmp/config.nix
@@ -6,8 +6,8 @@
   inherit (lib.modules) mkIf;
   inherit (lib.strings) optionalString;
   inherit (lib.generators) mkLuaInline;
-  inherit (lib.attrsets) attrValues filterAttrs;
-  inherit (lib.lists) map optional;
+  inherit (lib.attrsets) attrValues filterAttrs mapAttrsToList;
+  inherit (lib.lists) map optional elem;
   inherit (lib.nvim.lua) toLuaObject;
   inherit (builtins) concatStringsSep typeOf tryEval attrNames mapAttrs;
 
@@ -24,7 +24,22 @@
 
   enabledBlinkSources = filterAttrs (_source: definition: definition.enable) cfg.sourcePlugins;
   blinkSourcePlugins = map (definition: definition.package) (attrValues enabledBlinkSources);
+
+  blinkBuiltins = [
+    "path"
+    "lsp"
+    "snippets"
+    "buffer"
+    "omni"
+  ];
 in {
+  assertions =
+    mapAttrsToList (provider: definition: {
+      assertion = elem provider blinkBuiltins || definition.module != null;
+      message = "`config.vim.autocomplete.blink-cmp.setupOpts.sources.providers.${provider}.module` is `null`: non-builtin providers must set `module`.";
+    })
+    cfg.setupOpts.sources.providers;
+
   vim = mkIf cfg.enable {
     startPlugins = ["blink-compat"] ++ blinkSourcePlugins ++ (optional cfg.friendly-snippets.enable "friendly-snippets");
     lazy.plugins = {