diff --git a/command-line-arguments.c b/command-line-arguments.c
index 844d6c3d..c6f72696 100644
--- a/command-line-arguments.c
+++ b/command-line-arguments.c
@@ -23,7 +23,10 @@ _process_keyword_arg (const notmuch_opt_desc_t *arg_desc, char next, const char
     while (keywords->name) {
 	if (strcmp (arg_str, keywords->name) == 0) {
 	    if (arg_desc->output_var) {
-		*((int *)arg_desc->output_var) = keywords->value;
+		if (arg_desc->opt_type == NOTMUCH_OPT_KEYWORD_FLAGS)
+		    *((int *)arg_desc->output_var) |= keywords->value;
+		else
+		    *((int *)arg_desc->output_var) = keywords->value;
 	    }
 	    return TRUE;
 	}
@@ -152,6 +155,7 @@ parse_option (const char *arg,
 
 	switch (try->opt_type) {
 	case NOTMUCH_OPT_KEYWORD:
+	case NOTMUCH_OPT_KEYWORD_FLAGS:
 	    return _process_keyword_arg (try, next, value);
 	case NOTMUCH_OPT_BOOLEAN:
 	    return _process_boolean_arg (try, next, value);
diff --git a/command-line-arguments.h b/command-line-arguments.h
index de1734ad..6444129a 100644
--- a/command-line-arguments.h
+++ b/command-line-arguments.h
@@ -8,6 +8,7 @@ enum notmuch_opt_type {
     NOTMUCH_OPT_BOOLEAN,	/* --verbose              */
     NOTMUCH_OPT_INT,		/* --frob=8               */
     NOTMUCH_OPT_KEYWORD,	/* --format=raw|json|text */
+    NOTMUCH_OPT_KEYWORD_FLAGS,	/* the above with values OR'd together */
     NOTMUCH_OPT_STRING,		/* --file=/tmp/gnarf.txt  */
     NOTMUCH_OPT_POSITION	/* notmuch dump pos_arg   */
 };
diff --git a/test/T410-argument-parsing.sh b/test/T410-argument-parsing.sh
index 94e90874..2e5d7ae3 100755
--- a/test/T410-argument-parsing.sh
+++ b/test/T410-argument-parsing.sh
@@ -3,9 +3,10 @@ test_description="argument parsing"
 . ./test-lib.sh
 
 test_begin_subtest "sanity check"
-$TEST_DIRECTORY/arg-test  pos1  --keyword=one --string=foo pos2 --int=7 > OUTPUT
+$TEST_DIRECTORY/arg-test  pos1  --keyword=one --string=foo pos2 --int=7 --flag=one --flag=three > OUTPUT
 cat <<EOF > EXPECTED
 keyword 1
+flags 5
 int 7
 string foo
 positional arg 1 pos1
diff --git a/test/arg-test.c b/test/arg-test.c
index 6c49eacd..736686de 100644
--- a/test/arg-test.c
+++ b/test/arg-test.c
@@ -7,6 +7,7 @@ int main(int argc, char **argv){
     int opt_index=1;
 
     int kw_val=0;
+    int fl_val=0;
     int int_val=0;
     char *pos_arg1=NULL;
     char *pos_arg2=NULL;
@@ -17,6 +18,11 @@ int main(int argc, char **argv){
 	  (notmuch_keyword_t []){ { "one", 1 },
 				  { "two", 2 },
 				  { 0, 0 } } },
+	{ NOTMUCH_OPT_KEYWORD_FLAGS, &fl_val, "flag", 'f',
+	  (notmuch_keyword_t []){ { "one",   1 << 0},
+				  { "two",   1 << 1 },
+				  { "three", 1 << 2 },
+				  { 0, 0 } } },
 	{ NOTMUCH_OPT_INT, &int_val, "int", 'i', 0},
 	{ NOTMUCH_OPT_STRING, &string_val, "string", 's', 0},
 	{ NOTMUCH_OPT_POSITION, &pos_arg1, 0,0, 0},
@@ -31,6 +37,9 @@ int main(int argc, char **argv){
     if (kw_val)
 	printf("keyword %d\n", kw_val);
 
+    if (fl_val)
+	printf("flags %d\n", fl_val);
+
     if (int_val)
 	printf("int %d\n", int_val);