diff --git a/test/rule-syntax-check.py b/test/rule-syntax-check.py
index 4fa3042d4..4b602a925 100755
--- a/test/rule-syntax-check.py
+++ b/test/rule-syntax-check.py
@@ -28,7 +28,7 @@ if len(sys.argv) < 2:
 no_args_tests = re.compile('(ACTION|DEVPATH|KERNELS?|NAME|SYMLINK|SUBSYSTEMS?|DRIVERS?|TAG|RESULT|TEST)\s*(?:=|!)=\s*"([^"]*)"$')
 args_tests = re.compile('(ATTRS?|ENV|TEST){([a-zA-Z0-9/_.*%-]+)}\s*(?:=|!)=\s*"([^"]*)"$')
 no_args_assign = re.compile('(NAME|SYMLINK|OWNER|GROUP|MODE|TAG|PROGRAM|RUN|LABEL|GOTO|WAIT_FOR|OPTIONS|IMPORT)\s*(?:\+=|:=|=)\s*"([^"]*)"$')
-args_assign = re.compile('(ATTR|ENV|IMPORT|RUN){([a-zA-Z0-9/_.*%-]+)}\s*=\s*"([^"]*)"$')
+args_assign = re.compile('(ATTR|ENV|IMPORT|RUN){([a-zA-Z0-9/_.*%-]+)}\s*(=|\+=)\s*"([^"]*)"$')
 
 result = 0
 buffer = ''