diff --git a/src/node_env_var.cc b/src/node_env_var.cc
index 51dde17854ca41..00b175d73f1487 100644
--- a/src/node_env_var.cc
+++ b/src/node_env_var.cc
@@ -106,7 +106,7 @@ void RealEnvStore::Set(Isolate* isolate,
   node::Utf8Value val(isolate, value);
 
 #ifdef _WIN32
-  if (key[0] == L'=') return;
+  if (key.length() > 0 && key[0] == L'=') return;
 #endif
   uv_os_setenv(*key, *val);
 }
diff --git a/test/parallel/test-process-env.js b/test/parallel/test-process-env.js
index 0e06306634c3e2..4ece826e8b938f 100644
--- a/test/parallel/test-process-env.js
+++ b/test/parallel/test-process-env.js
@@ -106,3 +106,11 @@ if (common.isWindows) {
   const keys = Object.keys(process.env);
   assert.ok(keys.length > 0);
 }
+
+// Setting environment variables on Windows with empty names should not cause
+// an assertion failure.
+// https://github.com/nodejs/node/issues/32920
+{
+  process.env[''] = '';
+  assert.strictEqual(process.env[''], undefined);
+}