diff --git a/python/mozbuild/mozbuild/frontend/context.py b/python/mozbuild/mozbuild/frontend/context.py
index a51b01309af7..ed1c3aa8ed9c 100644
--- a/python/mozbuild/mozbuild/frontend/context.py
+++ b/python/mozbuild/mozbuild/frontend/context.py
@@ -591,13 +591,8 @@ class WasmFlags(TargetCompileFlags):
              ('WASM_CFLAGS', 'WASM_CXXFLAGS', 'WASM_LDFLAGS')),
             ('WARNINGS_AS_ERRORS', self._warnings_as_errors(),
              ('WASM_CXXFLAGS', 'WASM_CFLAGS', 'WASM_LDFLAGS')),
-            ('WARNINGS_CFLAGS',
-             context.config.substs.get('WARNINGS_CFLAGS'),
-             ('WASM_CFLAGS', 'WASM_LDFLAGS')),
             ('MOZBUILD_CFLAGS', None, ('WASM_CFLAGS',)),
             ('MOZBUILD_CXXFLAGS', None, ('WASM_CXXFLAGS',)),
-            ('COVERAGE', context.config.substs.get('COVERAGE_CFLAGS'),
-             ('WASM_CXXFLAGS', 'WASM_CFLAGS')),
             ('WASM_CFLAGS', context.config.substs.get('WASM_CFLAGS'),
              ('WASM_CFLAGS',)),
             ('WASM_CXXFLAGS', context.config.substs.get('WASM_CXXFLAGS'),