diff --git a/test/params_conversion_test.c b/test/params_conversion_test.c
index 1c3a4716a6a89c4689c6f2b72c0265f78eb78389..2fc17cc592058c8cb6fc6671c4d725df98b7e93b 100644
--- a/test/params_conversion_test.c
+++ b/test/params_conversion_test.c
@@ -19,6 +19,11 @@
 #  define strcasecmp _stricmp
 # endif
 
+# ifdef OPENSSL_SYS_VMS
+#  define strtoumax strtoull
+#  define strtoimax strtoll
+# endif
+
 typedef struct {
     OSSL_PARAM *param;
     int32_t i32;