3 files changed, 13 insertions, 3 deletions
diff --git a/t/interop/README b/t/interop/README
index 72d42bd856..4e0608f857 100644
--- a/t/interop/README
+++ b/t/interop/README
@@ -83,3 +83,10 @@ You can then use test_expect_success as usual, with a few differences:
      should create one with the appropriate version of git.
 
 At the end of the script, call test_done as usual.
+
+Some older versions may need a few build knobs tweaked (e.g., ancient
+versions of Git no longer build with modern OpenSSL). Your script can
+set MAKE_OPTS_A and MAKE_OPTS_B, which will be passed alongside
+GIT_INTEROP_MAKE_OPTS. Users can override them per-script by setting
+GIT_INTEROP_MAKE_OPTS_{A,B} in the environment, just like they can set
+GIT_TEST_VERSION_{A,B}.
diff --git a/t/interop/i5500-git-daemon.sh b/t/interop/i5500-git-daemon.sh
index 4d22e42f84..88712d1b5d 100755
--- a/t/interop/i5500-git-daemon.sh
+++ b/t/interop/i5500-git-daemon.sh
@@ -2,6 +2,7 @@
 
 VERSION_A=.
 VERSION_B=v1.0.0
+MAKE_OPTS_B="NO_OPENSSL=TooOld"
 
 : ${LIB_GIT_DAEMON_PORT:=5500}
 LIB_GIT_DAEMON_COMMAND='git.a daemon'
diff --git a/t/interop/interop-lib.sh b/t/interop/interop-lib.sh
index 62f4481b6e..1b5864d2a7 100644
--- a/t/interop/interop-lib.sh
+++ b/t/interop/interop-lib.sh
@@ -45,7 +45,7 @@ build_version () {
 
 	(
 		cd "$dir" &&
-		make $GIT_INTEROP_MAKE_OPTS >&2 &&
+		make $2 $GIT_INTEROP_MAKE_OPTS >&2 &&
 		touch .built
 	) || return 1
 
@@ -76,9 +76,11 @@ generate_wrappers () {
 
 VERSION_A=${GIT_TEST_VERSION_A:-$VERSION_A}
 VERSION_B=${GIT_TEST_VERSION_B:-$VERSION_B}
+MAKE_OPTS_A=${GIT_INTEROP_MAKE_OPTS_A:-$MAKE_OPTS_A}
+MAKE_OPTS_B=${GIT_INTEROP_MAKE_OPTS_B:-$MAKE_OPTS_B}
 
-if ! DIR_A=$(build_version "$VERSION_A") ||
-   ! DIR_B=$(build_version "$VERSION_B")
+if ! DIR_A=$(build_version "$VERSION_A" "$MAKE_OPTS_A") ||
+   ! DIR_B=$(build_version "$VERSION_B" "$MAKE_OPTS_B")
 then
 	echo >&2 "fatal: unable to build git versions"
 	exit 1