diff --git a/tests/diff3 b/tests/diff3
index b591751..e468243 100644
--- a/tests/diff3
+++ b/tests/diff3
@@ -30,12 +30,14 @@ EOF
 
 fail=0
 
-diff3 a b c > out 2> err || fail=1
+# Use --diff-program=diff since --program-transform-name and similar are
+# applied after 'make install'.
+diff3 --diff-program=diff a b c > out 2> err || fail=1
 compare exp out || fail=1
 compare /dev/null err || fail=1
 
 # Repeat, but with all three files the same:
-diff3 a a a > out 2> err || fail=1
+diff3 --diff-program=diff a a a > out 2> err || fail=1
 compare /dev/null out || fail=1
 compare /dev/null err || fail=1
 
@@ -101,7 +103,7 @@ cat <<'EOF' > exp40 || framework_failure_
   3z
 EOF
 
-diff3 d e f > out 2> err
+diff3 --diff-program=diff d e f > out 2> err
 compare exp40 out || fail=1
 compare /dev/null err || fail=1
 
diff --git a/tests/help-version b/tests/help-version
index 7dc84d7..e03acea 100755
--- a/tests/help-version
+++ b/tests/help-version
@@ -170,8 +170,12 @@ egrep_setup () { args="0 $tmp_in"; }
 fgrep_setup () { args="0 $tmp_in"; }
 
 diff_setup () { args="$tmp_in $tmp_in2"; }
-sdiff_setup () { args="$tmp_in $tmp_in2"; }
-diff3_setup () { args="$tmp_in $tmp_in2 $tmp_in2"; }
+
+# Use --diff-program=diff since --program-transform-name and similar are
+# applied after 'make install'.
+sdiff_setup () { args="--diff-program=diff $tmp_in $tmp_in2"; }
+diff3_setup () { args="--diff-program=diff $tmp_in $tmp_in2 $tmp_in2"; }
+
 cp_setup () { args="$tmp_in $tmp_in2"; }
 ln_setup () { args="$tmp_in ln-target"; }
 ginstall_setup () { args="$tmp_in $tmp_in2"; }