diff --git a/doc/api/cli.md b/doc/api/cli.md
index 41c747c1c3da75..f1b33e883ae883 100644
--- a/doc/api/cli.md
+++ b/doc/api/cli.md
@@ -372,7 +372,7 @@ Node options that are allowed are:
 
 V8 options that are allowed are:
 - `--abort-on-uncaught-exception`
-- `--max_old_space_size`
+- `--max-old-space-size`
 
 
 ### `NODE_REPL_HISTORY=file`
diff --git a/src/node.cc b/src/node.cc
index 98fde0dbbe3f65..2fd6da0c6f4c37 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -3786,15 +3786,34 @@ static void PrintHelp() {
 }
 
 
+static bool ArgIsAllowed(const char* arg, const char* allowed) {
+  for (; *arg && *allowed; arg++, allowed++) {
+    // Like normal strcmp(), except that a '_' in `allowed` matches either a '-'
+    // or '_' in `arg`.
+    if (*allowed == '_') {
+      if (!(*arg == '_' || *arg == '-'))
+        return false;
+    } else {
+      if (*arg != *allowed)
+        return false;
+    }
+  }
+
+  // "--some-arg=val" is allowed for "--some-arg"
+  if (*arg == '=')
+    return true;
+
+  // Both must be null, or one string is just a prefix of the other, not a
+  // match.
+  return !*arg && !*allowed;
+}
+
+
 static void CheckIfAllowedInEnv(const char* exe, bool is_env,
                                 const char* arg) {
   if (!is_env)
     return;
 
-  // Find the arg prefix when its --some_arg=val
-  const char* eq = strchr(arg, '=');
-  size_t arglen = eq ? eq - arg : strlen(arg);
-
   static const char* whitelist[] = {
     // Node options, sorted in `node --help` order for ease of comparison.
     "--require", "-r",
@@ -3820,14 +3839,14 @@ static void CheckIfAllowedInEnv(const char* exe, bool is_env,
     "--openssl-config",
     "--icu-data-dir",
 
-    // V8 options
-    "--abort-on-uncaught-exception",
+    // V8 options (define with '_', which allows '-' or '_')
+    "--abort_on_uncaught_exception",
     "--max_old_space_size",
   };
 
   for (unsigned i = 0; i < arraysize(whitelist); i++) {
     const char* allowed = whitelist[i];
-    if (strlen(allowed) == arglen && strncmp(allowed, arg, arglen) == 0)
+    if (ArgIsAllowed(arg, allowed))
       return;
   }
 
diff --git a/test/parallel/test-cli-node-options.js b/test/parallel/test-cli-node-options.js
index 104473bfa69e34..a1148fd0516703 100644
--- a/test/parallel/test-cli-node-options.js
+++ b/test/parallel/test-cli-node-options.js
@@ -26,6 +26,7 @@ disallow('--interactive');
 disallow('-i');
 disallow('--v8-options');
 disallow('--');
+disallow('--no_warnings'); // Node options don't allow '_' instead of '-'.
 
 function disallow(opt) {
   const options = {env: {NODE_OPTIONS: opt}};
@@ -43,6 +44,7 @@ const printA = require.resolve('../fixtures/printA.js');
 
 expect(`-r ${printA}`, 'A\nB\n');
 expect('--abort-on-uncaught-exception', 'B\n');
+expect('--abort_on_uncaught_exception', 'B\n');
 expect('--no-deprecation', 'B\n');
 expect('--no-warnings', 'B\n');
 expect('--trace-warnings', 'B\n');
@@ -61,6 +63,8 @@ expect('--icu-data-dir=_d', 'B\n');
 
 // V8 options
 expect('--max_old_space_size=0', 'B\n');
+expect('--max-old_space-size=0', 'B\n');
+expect('--max-old-space-size=0', 'B\n');
 
 function expect(opt, want) {
   const printB = require.resolve('../fixtures/printB.js');