diff --git a/tests/lang.sh b/tests/lang.sh
index bfb942d3d..75dbbc38e 100755
--- a/tests/lang.sh
+++ b/tests/lang.sh
@@ -52,9 +52,10 @@ for i in lang/parse-okay-*.nix; do
     i=$(basename "$i" .nix)
     if
         expect 0 nix-instantiate --parse - < "lang/$i.nix" \
-            1> >(sed "s!$(pwd)!/pwd!g" > "lang/$i.out") \
-            2> >(sed "s!$(pwd)!/pwd!g" > "lang/$i.err")
+            1> "lang/$i.out" \
+            2> "lang/$i.err"
     then
+        sed "s!$(pwd)!/pwd!g" "lang/$i.out" "lang/$i.err"
         diffAndAccept "$i" out exp
         diffAndAccept "$i" err err.exp
     else
diff --git a/tests/lang/framework.sh b/tests/lang/framework.sh
index d6499e0e9..516bff8ad 100644
--- a/tests/lang/framework.sh
+++ b/tests/lang/framework.sh
@@ -16,7 +16,7 @@ function diffAndAcceptInner() {
     fi
 
     # Diff so we get a nice message
-    if ! diff "$got" "$expectedOrEmpty"; then
+    if ! diff --unified "$got" "$expectedOrEmpty"; then
         echo "FAIL: evaluation result of $testName not as expected"
         badDiff=1
     fi