diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 9e5dc6c..94c339e 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -46,11 +46,22 @@
 : ${P_CLI:=../programs/ssl/ssl_client2}
 : ${P_PXY:=../programs/test/udp_proxy}
 : ${P_QUERY:=../programs/test/query_compile_time_config}
-: ${OPENSSL_CMD:=openssl} # OPENSSL would conflict with the build system
+: ${OPENSSL:=openssl}
 : ${GNUTLS_CLI:=gnutls-cli}
 : ${GNUTLS_SERV:=gnutls-serv}
 : ${PERL:=perl}
 
+# The OPENSSL variable used to be OPENSSL_CMD for historical reasons.
+# To help the migration, error out if the old variable is set,
+# but only if it has a different value than the new one.
+if [ "${OPENSSL_CMD+set}" = set ]; then
+    # the variable is set, we can now check its value
+    if [ "$OPENSSL_CMD" != "$OPENSSL" ]; then
+        echo "Please use OPENSSL instead of OPENSSL_CMD." >&2
+        exit 125
+    fi
+fi
+
 guess_config_name() {
     if git diff --quiet ../include/mbedtls/config.h 2>/dev/null; then
         echo "default"
@@ -62,8 +73,8 @@
 : ${MBEDTLS_TEST_CONFIGURATION:="$(guess_config_name)"}
 : ${MBEDTLS_TEST_PLATFORM:="$(uname -s | tr -c \\n0-9A-Za-z _)-$(uname -m | tr -c \\n0-9A-Za-z _)"}
 
-O_SRV="$OPENSSL_CMD s_server -www -cert data_files/server5.crt -key data_files/server5.key"
-O_CLI="echo 'GET / HTTP/1.0' | $OPENSSL_CMD s_client"
+O_SRV="$OPENSSL s_server -www -cert data_files/server5.crt -key data_files/server5.key"
+O_CLI="echo 'GET / HTTP/1.0' | $OPENSSL s_client"
 G_SRV="$GNUTLS_SERV --x509certfile data_files/server5.crt --x509keyfile data_files/server5.key"
 G_CLI="echo 'GET / HTTP/1.0' | $GNUTLS_CLI --x509cafile data_files/test-ca_cat12.crt"
 TCP_CLIENT="$PERL scripts/tcp_client.pl"
@@ -404,7 +415,7 @@
 # skip next test if OpenSSL doesn't support FALLBACK_SCSV
 requires_openssl_with_fallback_scsv() {
     if [ -z "${OPENSSL_HAS_FBSCSV:-}" ]; then
-        if $OPENSSL_CMD s_client -help 2>&1 | grep fallback_scsv >/dev/null
+        if $OPENSSL s_client -help 2>&1 | grep fallback_scsv >/dev/null
         then
             OPENSSL_HAS_FBSCSV="YES"
         else
@@ -1443,8 +1454,8 @@
         exit 1
     fi
 fi
-if which $OPENSSL_CMD >/dev/null 2>&1; then :; else
-    echo "Command '$OPENSSL_CMD' not found"
+if which $OPENSSL >/dev/null 2>&1; then :; else
+    echo "Command '$OPENSSL' not found"
     exit 1
 fi
 
@@ -1499,7 +1510,7 @@
 # OpenSSL 1.1.1f from Ubuntu 20.04. The syntax was only introduced in
 # OpenSSL 1.1.0 (21e0c1d23afff48601eb93135defddae51f7e2e3) and I can't find
 # a way to discover it from -help, so check the openssl version.
-case $($OPENSSL_CMD version) in
+case $($OPENSSL version) in
     "OpenSSL 0"*|"OpenSSL 1.0"*) :;;
     *)
         O_CLI="$O_CLI -cipher ALL@SECLEVEL=0"