diff --git a/nix/overlay.nix b/nix/overlay.nix
--- a/nix/overlay.nix
+++ b/nix/overlay.nix
@@ -28,9 +28,12 @@
   });
 
   olm = prev.olm.overrideAttrs(oldAttrs: {
-    # *.hh files aren't meant to be used externally, so we patch installation to add it
+    # *.hh files aren't meant to be used externally
+    # so we patch installation to add it
     postInstall = ''
-      cp $NIX_BUILD_TOP/${oldAttrs.src.name}/include/olm/*.h* ''${!outputDev}/include/olm
+      cp \
+        $NIX_BUILD_TOP/${oldAttrs.src.name}/include/olm/*.h* \
+        ''${!outputDev}/include/olm
     '';
   });
 }