diff --git a/pkgs/build-support/docker/nix-prefetch-docker b/pkgs/build-support/docker/nix-prefetch-docker
index bf01384ccdb4..1b6785189c28 100755
--- a/pkgs/build-support/docker/nix-prefetch-docker
+++ b/pkgs/build-support/docker/nix-prefetch-docker
@@ -12,7 +12,6 @@ finalImageTag=
 hashType=$NIX_HASH_ALGO
 hashFormat=$hashFormat
 format=nix
-skopeoCmd="skopeo --insecure-policy --tmpdir=$TMPDIR"
 
 usage(){
     echo  >&2 "syntax: nix-prefetch-docker [options] [IMAGE_NAME [IMAGE_TAG|IMAGE_DIGEST]]
@@ -39,7 +38,7 @@ get_image_digest(){
         imageTag="latest"
     fi
 
-    "$skopeoCmd" inspect "docker://$imageName:$imageTag" | jq '.Digest' -r
+    skopeo --insecure-policy --tmpdir=$TMPDIR inspect "docker://$imageName:$imageTag" | jq '.Digest' -r
 }
 
 get_name() {
@@ -128,9 +127,9 @@ trap "rm -rf \"$tmpPath\"" EXIT
 tmpFile="$tmpPath/$(get_name $finalImageName $finalImageTag)"
 
 if test -z "$QUIET"; then
-    "$skopeoCmd" --override-os ${os} --override-arch ${arch} copy "$sourceUrl" "docker-archive://$tmpFile:$finalImageName:$finalImageTag"
+    skopeo --insecure-policy --tmpdir=$TMPDIR --override-os ${os} --override-arch ${arch} copy "$sourceUrl" "docker-archive://$tmpFile:$finalImageName:$finalImageTag"
 else
-    "$skopeoCmd" --override-os ${os} --override-arch ${arch} copy "$sourceUrl" "docker-archive://$tmpFile:$finalImageName:$finalImageTag" > /dev/null
+    skopeo --insecure-policy --tmpdir=$TMPDIR --override-os ${os} --override-arch ${arch} copy "$sourceUrl" "docker-archive://$tmpFile:$finalImageName:$finalImageTag" > /dev/null
 fi
 
 # Compute the hash.