diff --git a/nixos/modules/services/editors/emacs.nix b/nixos/modules/services/editors/emacs.nix
index 6795ec52fe4d..08fa6de6374c 100644
--- a/nixos/modules/services/editors/emacs.nix
+++ b/nixos/modules/services/editors/emacs.nix
@@ -79,9 +79,13 @@ in {
 
     environment.systemPackages = [ cfg.package editorScript ];
 
-    environment.variables = if cfg.defaultEditor then {
-      EDITOR = mkOverride 900 "${editorScript}/bin/emacseditor";
-    } else {};
+    environment.variables = {
+      # This is required so that GTK applications launched from Emacs
+      # get properly themed:
+      GTK_DATA_PREFIX = "${config.system.path}";
+    } // (if cfg.defaultEditor then {
+        EDITOR = mkOverride 900 "${editorScript}/bin/emacseditor";
+      } else {});
   };
 
   meta.doc = ./emacs.xml;