diff --git a/pkgs/os-specific/linux/kernel/manual-config.nix b/pkgs/os-specific/linux/kernel/manual-config.nix
index 41d23aa13240..cd207f1d610c 100644
--- a/pkgs/os-specific/linux/kernel/manual-config.nix
+++ b/pkgs/os-specific/linux/kernel/manual-config.nix
@@ -32,24 +32,18 @@ let
 
   readConfig =
     configfile:
-    lib.listToAttrs (
-      map
-        (
-          line:
-          let
-            match = lib.match "(.*)=\"?(.*)\"?" line;
-          in
-          {
-            name = lib.elemAt match 0;
-            value = lib.elemAt match 1;
-          }
-        )
-        (
-          lib.filter (line: !(lib.hasPrefix "#" line || line == "")) (
-            lib.splitString "\n" (builtins.readFile configfile)
-          )
-        )
-    );
+    let
+      matchLine =
+        line:
+        let
+          match = lib.match "(CONFIG_[^=]+)=([ym])" line;
+        in
+        lib.optional (match != null) {
+          name = lib.elemAt match 0;
+          value = lib.elemAt match 1;
+        };
+    in
+    lib.listToAttrs (lib.concatMap matchLine (lib.splitString "\n" (builtins.readFile configfile)));
 in
 lib.makeOverridable (
   {