diff --git a/platformio/builder/tools/platformio.py b/platformio/builder/tools/platformio.py
index 9198c751..bb2dd1c6 100644
--- a/platformio/builder/tools/platformio.py
+++ b/platformio/builder/tools/platformio.py
@@ -176,8 +176,6 @@ def ProcessUnFlags(env, flags):
         return
     for key, unflags in env.ParseFlagsExtended(flags).items():
         for unflag in unflags:
-            if not isinstance(unflag, (list, tuple)):
-                unflag = tuple([unflag])
             for current in env.get(key, []):
                 conditions = [
                     unflag == current,
diff --git a/tests/test_builder.py b/tests/test_builder.py
index 6dd90eb7..cafd1cee 100644
--- a/tests/test_builder.py
+++ b/tests/test_builder.py
@@ -63,7 +63,7 @@ def test_build_unflags(clirunner, validate_cliresult, tmpdir):
     tmpdir.join("platformio.ini").write("""
 [env:native]
 platform = native
-build_unflags = -DTMP_MACRO1=45 -I. -DNON_EXISTING_MACRO
+build_unflags = -DTMP_MACRO1=45 -I. -DNON_EXISTING_MACRO -lunknownLib -Os
 extra_scripts = pre:extra.py
 """)
 
@@ -73,6 +73,8 @@ env.Append(CPPPATH="%s")
 env.Append(CPPDEFINES="TMP_MACRO1")
 env.Append(CPPDEFINES=["TMP_MACRO2"])
 env.Append(CPPDEFINES=("TMP_MACRO3", 13))
+env.Append(CCFLAGS=["-Os"])
+env.Append(LIBS=["unknownLib"])
     """ % str(tmpdir))
 
     tmpdir.mkdir("src").join("main.c").write("""
@@ -90,4 +92,5 @@ int main() {
     build_output = result.output[result.output.find(
         "Scanning dependencies..."):]
     assert "-DTMP_MACRO1" not in build_output
+    assert "-Os" not in build_output
     assert str(tmpdir) not in build_output