diff --git a/tests/flakes.sh b/tests/flakes.sh
index 41f123883..283c2e397 100644
--- a/tests/flakes.sh
+++ b/tests/flakes.sh
@@ -114,52 +114,52 @@ cat > $registry <<EOF
 EOF
 
 # Test 'nix flake list'.
-(( $(nix flake list --flake-registry $registry | wc -l) == 6 ))
+(( $(nix flake list | wc -l) == 6 ))
 
 # Test 'nix flake info'.
-nix flake info --flake-registry $registry flake1 | grep -q 'URL: .*flake1.*'
+nix flake info flake1 | grep -q 'URL: .*flake1.*'
 
 # Test 'nix flake info' on a local flake.
-(cd $flake1Dir && nix flake info --flake-registry $registry) | grep -q 'URL: .*flake1.*'
-(cd $flake1Dir && nix flake info --flake-registry $registry .) | grep -q 'URL: .*flake1.*'
-nix flake info --flake-registry $registry $flake1Dir | grep -q 'URL: .*flake1.*'
+(cd $flake1Dir && nix flake info) | grep -q 'URL: .*flake1.*'
+(cd $flake1Dir && nix flake info .) | grep -q 'URL: .*flake1.*'
+nix flake info $flake1Dir | grep -q 'URL: .*flake1.*'
 
 # Test 'nix flake info --json'.
-json=$(nix flake info --flake-registry $registry flake1 --json | jq .)
+json=$(nix flake info flake1 --json | jq .)
 [[ $(echo "$json" | jq -r .description) = 'Bla bla' ]]
 [[ -d $(echo "$json" | jq -r .path) ]]
 [[ $(echo "$json" | jq -r .lastModified) = $(git -C $flake1Dir log -n1 --format=%ct) ]]
 
 # Test 'nix build' on a flake.
-nix build -o $TEST_ROOT/result --flake-registry $registry flake1#foo
+nix build -o $TEST_ROOT/result flake1#foo
 [[ -e $TEST_ROOT/result/hello ]]
 
 # Test defaultPackage.
-nix build -o $TEST_ROOT/result --flake-registry $registry flake1
+nix build -o $TEST_ROOT/result flake1
 [[ -e $TEST_ROOT/result/hello ]]
 
-nix build -o $TEST_ROOT/result --flake-registry $registry $flake1Dir
-nix build -o $TEST_ROOT/result --flake-registry $registry git+file://$flake1Dir
+nix build -o $TEST_ROOT/result $flake1Dir
+nix build -o $TEST_ROOT/result git+file://$flake1Dir
 
 # Check that store symlinks inside a flake are not interpreted as flakes.
-nix build -o $flake1Dir/result --flake-registry $registry git+file://$flake1Dir
+nix build -o $flake1Dir/result git+file://$flake1Dir
 nix path-info $flake1Dir/result
 
 # Building a flake with an unlocked dependency should fail in pure mode.
-(! nix build -o $TEST_ROOT/result --flake-registry $registry flake2#bar --no-registries)
+(! nix build -o $TEST_ROOT/result flake2#bar --no-registries)
 (! nix eval --expr "builtins.getFlake \"$flake2Dir\"")
 
 # But should succeed in impure mode.
-nix build -o $TEST_ROOT/result --flake-registry $registry flake2#bar --impure
+nix build -o $TEST_ROOT/result flake2#bar --impure
 
 # Test automatic lock file generation.
-nix build -o $TEST_ROOT/result --flake-registry $registry $flake2Dir#bar
+nix build -o $TEST_ROOT/result $flake2Dir#bar
 [[ -e $flake2Dir/flake.lock ]]
 git -C $flake2Dir add flake.lock
 git -C $flake2Dir commit flake.lock -m 'Add flake.lock'
 
 # Rerunning the build should not change the lockfile.
-nix build -o $TEST_ROOT/result --flake-registry $registry $flake2Dir#bar
+nix build -o $TEST_ROOT/result $flake2Dir#bar
 [[ -z $(git -C $flake2Dir diff master) ]]
 
 # Building with a lockfile should not require a fetch of the registry.
@@ -167,18 +167,17 @@ nix build -o $TEST_ROOT/result --flake-registry file:///no-registry.json $flake2
 nix build -o $TEST_ROOT/result --no-registries $flake2Dir#bar --tarball-ttl 0
 
 # Updating the flake should not change the lockfile.
-nix flake update --flake-registry $registry $flake2Dir
+nix flake update $flake2Dir
 [[ -z $(git -C $flake2Dir diff master) ]]
 
 # Now we should be able to build the flake in pure mode.
-nix build -o $TEST_ROOT/result --flake-registry $registry flake2#bar
+nix build -o $TEST_ROOT/result flake2#bar
 
 # Or without a registry.
-# FIXME: shouldn't need '--flake-registry /no-registry'?
-nix build -o $TEST_ROOT/result --flake-registry /no-registry git+file://$flake2Dir#bar --tarball-ttl 0
+nix build -o $TEST_ROOT/result --no-registries git+file://$flake2Dir#bar --tarball-ttl 0
 
 # Test whether indirect dependencies work.
-nix build -o $TEST_ROOT/result --flake-registry $registry $flake3Dir#xyzzy
+nix build -o $TEST_ROOT/result $flake3Dir#xyzzy
 git -C $flake3Dir add flake.lock
 
 # Add dependency to flake3.
@@ -201,8 +200,8 @@ git -C $flake3Dir add flake.nix
 git -C $flake3Dir commit -m 'Update flake.nix'
 
 # Check whether `nix build` works with an incomplete lockfile
-nix build -o $TEST_ROOT/result --flake-registry $registry $flake3Dir#"sth sth"
-nix build -o $TEST_ROOT/result --flake-registry $registry $flake3Dir#"sth%20sth"
+nix build -o $TEST_ROOT/result $flake3Dir#"sth sth"
+nix build -o $TEST_ROOT/result $flake3Dir#"sth%20sth"
 
 # Check whether it saved the lockfile
 (! [[ -z $(git -C $flake3Dir diff master) ]])
@@ -213,7 +212,7 @@ git -C $flake3Dir commit -m 'Add lockfile'
 
 # Unsupported editions should be an error.
 sed -i $flake3Dir/flake.nix -e s/201909/201912/
-nix build -o $TEST_ROOT/result --flake-registry $registry $flake3Dir#sth 2>&1 | grep 'unsupported edition'
+nix build -o $TEST_ROOT/result $flake3Dir#sth 2>&1 | grep 'unsupported edition'
 
 # Test whether registry caching works.
 nix flake list --flake-registry file://$registry | grep -q flake3
@@ -224,12 +223,12 @@ mv $registry.tmp $registry
 # Test whether flakes are registered as GC roots for offline use.
 # FIXME: use tarballs rather than git.
 rm -rf $TEST_HOME/.cache
-_NIX_FORCE_HTTP=1 nix build -o $TEST_ROOT/result --flake-registry file://$registry git+file://$flake2Dir#bar
+_NIX_FORCE_HTTP=1 nix build -o $TEST_ROOT/result git+file://$flake2Dir#bar
 mv $flake1Dir $flake1Dir.tmp
 mv $flake2Dir $flake2Dir.tmp
 nix-store --gc
-_NIX_FORCE_HTTP=1 nix build -o $TEST_ROOT/result --flake-registry file://$registry git+file://$flake2Dir#bar
-_NIX_FORCE_HTTP=1 nix build -o $TEST_ROOT/result --flake-registry file://$registry git+file://$flake2Dir#bar --tarball-ttl 0
+_NIX_FORCE_HTTP=1 nix build -o $TEST_ROOT/result git+file://$flake2Dir#bar
+_NIX_FORCE_HTTP=1 nix build -o $TEST_ROOT/result git+file://$flake2Dir#bar --tarball-ttl 0
 mv $flake1Dir.tmp $flake1Dir
 mv $flake2Dir.tmp $flake2Dir
 
@@ -274,13 +273,13 @@ git -C $flake3Dir commit -m 'Add nonFlakeInputs'
 
 # Check whether `nix build` works with a lockfile which is missing a
 # nonFlakeInputs.
-nix build -o $TEST_ROOT/result --flake-registry $registry $flake3Dir#sth
+nix build -o $TEST_ROOT/result $flake3Dir#sth
 
 git -C $flake3Dir add flake.lock
 
 git -C $flake3Dir commit -m 'Update nonFlakeInputs'
 
-nix build -o $TEST_ROOT/result --flake-registry $registry flake3#fnord
+nix build -o $TEST_ROOT/result flake3#fnord
 [[ $(cat $TEST_ROOT/result) = FNORD ]]
 
 # Check whether flake input fetching is lazy: flake3#sth does not
@@ -289,21 +288,21 @@ rm -rf $TEST_HOME/.cache
 clearStore
 mv $flake2Dir $flake2Dir.tmp
 mv $nonFlakeDir $nonFlakeDir.tmp
-nix build -o $TEST_ROOT/result --flake-registry $registry flake3#sth
-(! nix build -o $TEST_ROOT/result --flake-registry $registry flake3#xyzzy)
-(! nix build -o $TEST_ROOT/result --flake-registry $registry flake3#fnord)
+nix build -o $TEST_ROOT/result flake3#sth
+(! nix build -o $TEST_ROOT/result flake3#xyzzy)
+(! nix build -o $TEST_ROOT/result flake3#fnord)
 mv $flake2Dir.tmp $flake2Dir
 mv $nonFlakeDir.tmp $nonFlakeDir
-nix build -o $TEST_ROOT/result --flake-registry $registry flake3#xyzzy flake3#fnord
+nix build -o $TEST_ROOT/result flake3#xyzzy flake3#fnord
 
 # Test doing multiple `lookupFlake`s
-nix build -o $TEST_ROOT/result --flake-registry $registry flake4#xyzzy
+nix build -o $TEST_ROOT/result flake4#xyzzy
 
 # Test 'nix flake update' and --override-flake.
-nix flake update --flake-registry $registry $flake3Dir
+nix flake update $flake3Dir
 [[ -z $(git -C $flake3Dir diff master) ]]
 
-nix flake update --flake-registry $registry $flake3Dir --recreate-lock-file --override-flake flake2 nixpkgs
+nix flake update $flake3Dir --recreate-lock-file --override-flake flake2 nixpkgs
 [[ ! -z $(git -C $flake3Dir diff master) ]]
 
 # Make branch "removeXyzzy" where flake3 doesn't have xyzzy anymore
@@ -342,29 +341,29 @@ git -C $flake3Dir commit -m 'Remove packages.xyzzy'
 git -C $flake3Dir checkout master
 
 # Test whether fuzzy-matching works for IsAlias
-(! nix build -o $TEST_ROOT/result --flake-registry $registry flake4/removeXyzzy#xyzzy)
+(! nix build -o $TEST_ROOT/result flake4/removeXyzzy#xyzzy)
 
 # Test whether fuzzy-matching works for IsGit
-(! nix build -o $TEST_ROOT/result --flake-registry $registry flake4/removeXyzzy#xyzzy)
-nix build -o $TEST_ROOT/result --flake-registry $registry flake4/removeXyzzy#sth
+(! nix build -o $TEST_ROOT/result flake4/removeXyzzy#xyzzy)
+nix build -o $TEST_ROOT/result flake4/removeXyzzy#sth
 
 # Testing the nix CLI
-nix flake add --flake-registry $registry flake1 flake3
-(( $(nix flake list --flake-registry $registry | wc -l) == 7 ))
-nix flake pin --flake-registry $registry flake1
-(( $(nix flake list --flake-registry $registry | wc -l) == 7 ))
-nix flake remove --flake-registry $registry flake1
-(( $(nix flake list --flake-registry $registry | wc -l) == 6 ))
+nix flake add flake1 flake3
+(( $(nix flake list | wc -l) == 7 ))
+nix flake pin flake1
+(( $(nix flake list | wc -l) == 7 ))
+nix flake remove flake1
+(( $(nix flake list | wc -l) == 6 ))
 
 # Test 'nix flake init'.
 (cd $flake7Dir && nix flake init)
 git -C $flake7Dir add flake.nix
-nix flake --flake-registry $registry check $flake7Dir
+nix flake check $flake7Dir
 git -C $flake7Dir commit -m 'Initial'
 
 # Test 'nix flake clone'.
 rm -rf $TEST_ROOT/flake1-v2
-nix flake clone --flake-registry $registry flake1 --dest $TEST_ROOT/flake1-v2
+nix flake clone flake1 --dest $TEST_ROOT/flake1-v2
 [ -e $TEST_ROOT/flake1-v2/flake.nix ]
 
 # More 'nix flake check' tests.
@@ -379,7 +378,7 @@ cat > $flake3Dir/flake.nix <<EOF
 }
 EOF
 
-nix flake check --flake-registry $registry $flake3Dir
+nix flake check $flake3Dir
 
 cat > $flake3Dir/flake.nix <<EOF
 {
@@ -392,7 +391,7 @@ cat > $flake3Dir/flake.nix <<EOF
 }
 EOF
 
-(! nix flake check --flake-registry $registry $flake3Dir)
+(! nix flake check $flake3Dir)
 
 cat > $flake3Dir/flake.nix <<EOF
 {
@@ -407,7 +406,7 @@ cat > $flake3Dir/flake.nix <<EOF
 }
 EOF
 
-nix flake check --flake-registry $registry $flake3Dir
+nix flake check $flake3Dir
 
 cat > $flake3Dir/flake.nix <<EOF
 {
@@ -422,7 +421,7 @@ cat > $flake3Dir/flake.nix <<EOF
 }
 EOF
 
-(! nix flake check --flake-registry $registry $flake3Dir)
+(! nix flake check $flake3Dir)
 
 cat > $flake3Dir/flake.nix <<EOF
 {
@@ -436,7 +435,7 @@ cat > $flake3Dir/flake.nix <<EOF
 }
 EOF
 
-nix flake check --flake-registry $registry $flake3Dir
+nix flake check $flake3Dir
 
 cat > $flake3Dir/flake.nix <<EOF
 {
@@ -450,7 +449,7 @@ cat > $flake3Dir/flake.nix <<EOF
 }
 EOF
 
-(! nix flake check --flake-registry $registry $flake3Dir)
+(! nix flake check $flake3Dir)
 
 # Test 'follows' inputs.
 cat > $flake3Dir/flake.nix <<EOF
@@ -465,7 +464,7 @@ cat > $flake3Dir/flake.nix <<EOF
 }
 EOF
 
-nix flake update --flake-registry $registry $flake3Dir
+nix flake update $flake3Dir
 [[ $(jq .inputs.foo.url $flake3Dir/flake.lock) = $(jq .inputs.bar.url $flake3Dir/flake.lock) ]]
 
 cat > $flake3Dir/flake.nix <<EOF
@@ -479,7 +478,7 @@ cat > $flake3Dir/flake.nix <<EOF
 }
 EOF
 
-nix flake update --flake-registry $registry $flake3Dir
+nix flake update $flake3Dir
 [[ $(jq .inputs.bar.url $flake3Dir/flake.lock) =~ flake1 ]]
 
 cat > $flake3Dir/flake.nix <<EOF
@@ -493,7 +492,7 @@ cat > $flake3Dir/flake.nix <<EOF
 }
 EOF
 
-nix flake update --flake-registry $registry $flake3Dir
+nix flake update $flake3Dir
 [[ $(jq .inputs.bar.url $flake3Dir/flake.lock) =~ flake2 ]]
 
 # Test overriding inputs of inputs.
@@ -508,7 +507,7 @@ cat > $flake3Dir/flake.nix <<EOF
 }
 EOF
 
-nix flake update --flake-registry $registry $flake3Dir
+nix flake update $flake3Dir
 [[ $(jq .inputs.flake2.inputs.flake1.url $flake3Dir/flake.lock) =~ flake7 ]]
 
 cat > $flake3Dir/flake.nix <<EOF
@@ -523,7 +522,7 @@ cat > $flake3Dir/flake.nix <<EOF
 }
 EOF
 
-nix flake update --flake-registry $registry $flake3Dir --recreate-lock-file
+nix flake update $flake3Dir --recreate-lock-file
 [[ $(jq .inputs.flake2.inputs.flake1.url $flake3Dir/flake.lock) =~ flake7 ]]
 
 # Test Mercurial flakes.
@@ -550,27 +549,27 @@ EOF
 hg add $flake5Dir/flake.nix
 hg commit --config ui.username=foobar@example.org $flake5Dir -m 'Initial commit'
 
-nix build -o $TEST_ROOT/result --flake-registry $registry hg+file://$flake5Dir
+nix build -o $TEST_ROOT/result hg+file://$flake5Dir
 [[ -e $TEST_ROOT/result/hello ]]
 
-nix flake info --flake-registry $registry --json hg+file://$flake5Dir | jq -e -r .revision
+nix flake info --json hg+file://$flake5Dir | jq -e -r .revision
 
 # This will fail because flake.lock is not tracked by Mercurial.
-(! nix eval --flake-registry $registry hg+file://$flake5Dir#expr)
+(! nix eval hg+file://$flake5Dir#expr)
 
 hg add $flake5Dir/flake.lock
 
-nix eval --flake-registry $registry hg+file://$flake5Dir#expr
+nix eval hg+file://$flake5Dir#expr
 
-(! nix eval --flake-registry $registry hg+file://$flake5Dir#expr --no-allow-dirty)
+(! nix eval hg+file://$flake5Dir#expr --no-allow-dirty)
 
-(! nix flake info --flake-registry $registry --json hg+file://$flake5Dir | jq -e -r .revision)
+(! nix flake info --json hg+file://$flake5Dir | jq -e -r .revision)
 
 hg commit --config ui.username=foobar@example.org $flake5Dir -m 'Add lock file'
 
-nix flake info --flake-registry $registry --json hg+file://$flake5Dir --refresh | jq -e -r .revision
-nix flake info --flake-registry $registry --json hg+file://$flake5Dir
-[[ $(nix flake info --flake-registry $registry --json hg+file://$flake5Dir | jq -e -r .revCount) = 1 ]]
+nix flake info --json hg+file://$flake5Dir --refresh | jq -e -r .revision
+nix flake info --json hg+file://$flake5Dir
+[[ $(nix flake info --json hg+file://$flake5Dir | jq -e -r .revCount) = 1 ]]
 
 nix build -o $TEST_ROOT/result hg+file://$flake5Dir --no-registries --no-allow-dirty
 
diff --git a/tests/init.sh b/tests/init.sh
index c62c4856a..90f1bdcb6 100644
--- a/tests/init.sh
+++ b/tests/init.sh
@@ -18,6 +18,7 @@ build-users-group =
 keep-derivations = false
 sandbox = false
 experimental-features = nix-command flakes
+flake-registry = $TEST_ROOT/registry.json
 include nix.conf.extra
 EOF