diff --git a/platformio/managers/package.py b/platformio/managers/package.py
index ba7fb494..de87904b 100644
--- a/platformio/managers/package.py
+++ b/platformio/managers/package.py
@@ -79,7 +79,7 @@ class PkgRepoMixin(object):
 
     @staticmethod
     def is_system_compatible(valid_systems):
-        if valid_systems in (None, "all", "*"):
+        if not valid_systems or "*" in valid_systems:
             return True
         if not isinstance(valid_systems, list):
             valid_systems = list([valid_systems])
diff --git a/platformio/package/manifest/parser.py b/platformio/package/manifest/parser.py
index fb6f06db..22c21b7b 100644
--- a/platformio/package/manifest/parser.py
+++ b/platformio/package/manifest/parser.py
@@ -537,7 +537,7 @@ class PackageJsonManifestParser(BaseManifestParser):
     def _parse_system(data):
         if "system" not in data:
             return data
-        if data["system"] in ("*", ["*"]):
+        if data["system"] in ("*", ["*"], "all"):
             del data["system"]
             return data
         if not isinstance(data["system"], list):
diff --git a/tests/test_pkgmanifest.py b/tests/test_pkgmanifest.py
index f779b488..18078a7f 100644
--- a/tests/test_pkgmanifest.py
+++ b/tests/test_pkgmanifest.py
@@ -479,6 +479,11 @@ def test_package_json_schema():
     )
     assert "system" not in mp.as_dict()
 
+    mp = parser.ManifestParserFactory.new(
+        '{"system": "all"}', parser.ManifestFileType.PACKAGE_JSON
+    )
+    assert "system" not in mp.as_dict()
+
     mp = parser.ManifestParserFactory.new(
         '{"system": "darwin_x86_64"}', parser.ManifestFileType.PACKAGE_JSON
     )