diff --git a/config/rules.mk b/config/rules.mk
index 352a9663cf9db..d1412acd8f32a 100644
--- a/config/rules.mk
+++ b/config/rules.mk
@@ -936,7 +936,7 @@ endif
 endif
 
 libs realchrome:: $(FINAL_TARGET)/chrome
-	$(call py_action,jar_maker,\
+	$(call py3_action,jar_maker,\
 	  $(QUIET) -d $(FINAL_TARGET) \
 	  $(MAKE_JARS_FLAGS) $(DEFINES) $(ACDEFINES) \
 	  $(JAR_MANIFEST))
diff --git a/python/mozbuild/mozbuild/jar.py b/python/mozbuild/mozbuild/jar.py
index 6684a0b2f2f19..8d6d4aa5c2171 100644
--- a/python/mozbuild/mozbuild/jar.py
+++ b/python/mozbuild/mozbuild/jar.py
@@ -49,7 +49,7 @@ def __init__(self, name, zipfile):
     def write(self, content):
         '''Append the given content to this zip entry'''
 
-        self._inner.write(content)
+        self._inner.write(ensure_bytes(content))
         return
 
     def close(self):