diff --git a/tests/check.sh b/tests/check.sh
index 5f25d04cb2ca17d3fb385b216954a98658d7e79b..5f4997e287c349059e9c20800b98b6c31f82faed 100644
--- a/tests/check.sh
+++ b/tests/check.sh
@@ -61,30 +61,30 @@ nix-build check.nix -A nondeterministic --no-out-link --repeat 1 2> $TEST_ROOT/l
 [ "$status" = "1" ]
 grep 'differs from previous round' $TEST_ROOT/log
 
-path=$(nix-build check.nix -A fetchurl --no-out-link --hashed-mirrors '')
+path=$(nix-build check.nix -A fetchurl --no-out-link)
 
 chmod +w $path
 echo foo > $path
 chmod -w $path
 
-nix-build check.nix -A fetchurl --no-out-link --check --hashed-mirrors ''
+nix-build check.nix -A fetchurl --no-out-link --check
 # Note: "check" doesn't repair anything, it just compares to the hash stored in the database.
 [[ $(cat $path) = foo ]]
 
-nix-build check.nix -A fetchurl --no-out-link --repair --hashed-mirrors ''
+nix-build check.nix -A fetchurl --no-out-link --repair
 [[ $(cat $path) != foo ]]
 
-nix-build check.nix -A hashmismatch --no-out-link --hashed-mirrors '' || status=$?
+nix-build check.nix -A hashmismatch --no-out-link || status=$?
 [ "$status" = "102" ]
 
 echo -n > ./dummy
-nix-build check.nix -A hashmismatch --no-out-link --hashed-mirrors ''
+nix-build check.nix -A hashmismatch --no-out-link
 echo 'Hello World' > ./dummy
 
-nix-build check.nix -A hashmismatch --no-out-link --check --hashed-mirrors '' || status=$?
+nix-build check.nix -A hashmismatch --no-out-link --check || status=$?
 [ "$status" = "102" ]
 
 # Multiple failures with --keep-going
 nix-build check.nix -A nondeterministic --no-out-link
-nix-build check.nix -A nondeterministic -A hashmismatch --no-out-link --check --keep-going --hashed-mirrors '' || status=$?
+nix-build check.nix -A nondeterministic -A hashmismatch --no-out-link --check --keep-going || status=$?
 [ "$status" = "110" ]
diff --git a/tests/fetchurl.sh b/tests/fetchurl.sh
index 2535651b09a49f405ce3ebd8396eb4d1ff926a2e..13447d774d24ceb3dd09f9843783c9ad1302d604 100644
--- a/tests/fetchurl.sh
+++ b/tests/fetchurl.sh
@@ -5,7 +5,7 @@ clearStore
 # Test fetching a flat file.
 hash=$(nix-hash --flat --type sha256 ./fetchurl.sh)
 
-outPath=$(nix-build '<nix/fetchurl.nix>' --argstr url file://$(pwd)/fetchurl.sh --argstr sha256 $hash --no-out-link --hashed-mirrors '')
+outPath=$(nix-build '<nix/fetchurl.nix>' --argstr url file://$(pwd)/fetchurl.sh --argstr sha256 $hash --no-out-link)
 
 cmp $outPath fetchurl.sh
 
@@ -14,7 +14,7 @@ clearStore
 
 hash=$(nix hash-file --type sha512 --base64 ./fetchurl.sh)
 
-outPath=$(nix-build '<nix/fetchurl.nix>' --argstr url file://$(pwd)/fetchurl.sh --argstr sha512 $hash --no-out-link --hashed-mirrors '')
+outPath=$(nix-build '<nix/fetchurl.nix>' --argstr url file://$(pwd)/fetchurl.sh --argstr sha512 $hash --no-out-link)
 
 cmp $outPath fetchurl.sh
 
@@ -25,26 +25,23 @@ hash=$(nix hash-file ./fetchurl.sh)
 
 [[ $hash =~ ^sha256- ]]
 
-outPath=$(nix-build '<nix/fetchurl.nix>' --argstr url file://$(pwd)/fetchurl.sh --argstr hash $hash --no-out-link --hashed-mirrors '')
+outPath=$(nix-build '<nix/fetchurl.nix>' --argstr url file://$(pwd)/fetchurl.sh --argstr hash $hash --no-out-link)
 
 cmp $outPath fetchurl.sh
 
-# Test the hashed mirror feature.
+# Test that we can substitute from a different store dir.
 clearStore
 
-hash=$(nix hash-file --type sha512 --base64 ./fetchurl.sh)
-hash32=$(nix hash-file --type sha512 --base16 ./fetchurl.sh)
+other_store=file://$TEST_ROOT/other_store
 
-mirror=$TEST_ROOT/hashed-mirror
-rm -rf $mirror
-mkdir -p $mirror/sha512
-ln -s $(pwd)/fetchurl.sh $mirror/sha512/$hash32
+hash=$(nix hash-file --type sha256 --base16 ./fetchurl.sh)
+storePath=$(nix add-to-store --store $other_store ./fetchurl.sh)
 
-outPath=$(nix-build '<nix/fetchurl.nix>' --argstr url file:///no-such-dir/fetchurl.sh --argstr sha512 $hash --no-out-link --hashed-mirrors "file://$mirror")
+outPath=$(nix-build -vvvvvv '<nix/fetchurl.nix>' --argstr url file:///no-such-dir/fetchurl.sh --argstr sha256 $hash --no-out-link --substituters $other_store)
 
 # Test hashed mirrors with an SRI hash.
 nix-build '<nix/fetchurl.nix>' --argstr url file:///no-such-dir/fetchurl.sh --argstr hash $(nix to-sri --type sha512 $hash) \
-          --argstr name bla --no-out-link --hashed-mirrors "file://$mirror"
+          --argstr name bla --no-out-link --substituters $other_store
 
 # Test unpacking a NAR.
 rm -rf $TEST_ROOT/archive