diff --git a/tests/functional/compression-levels.sh b/tests/functional/compression-levels.sh
index 34f66c531..6a2111f10 100755
--- a/tests/functional/compression-levels.sh
+++ b/tests/functional/compression-levels.sh
@@ -9,16 +9,16 @@ outPath=$(nix-build dependencies.nix --no-out-link)
 
 cacheURI="file://$cacheDir?compression=xz&compression-level=0"
 
-nix copy --to $cacheURI $outPath
+nix copy --to "$cacheURI" "$outPath"
 
-FILESIZES=$(cat ${cacheDir}/*.narinfo | awk '/FileSize: /{sum+=$2}END{print sum}')
+FILESIZES=$(cat "${cacheDir}"/*.narinfo | awk '/FileSize: /{sum+=$2}END{print sum}')
 
 clearCache
 
 cacheURI="file://$cacheDir?compression=xz&compression-level=5"
 
-nix copy --to $cacheURI $outPath
+nix copy --to "$cacheURI" "$outPath"
 
-FILESIZES2=$(cat ${cacheDir}/*.narinfo | awk '/FileSize: /{sum+=$2}END{print sum}')
+FILESIZES2=$(cat "${cacheDir}"/*.narinfo | awk '/FileSize: /{sum+=$2}END{print sum}')
 
 [[ $FILESIZES -gt $FILESIZES2 ]]