diff --git a/date.c b/date.c
index 54c709e4a0..68a260c214 100644
--- a/date.c
+++ b/date.c
@@ -993,6 +993,11 @@ void parse_date_format(const char *format, struct date_mode *mode)
 		die("unknown date format %s", format);
 }
 
+void date_mode_release(struct date_mode *mode)
+{
+	free((char *)mode->strftime_fmt);
+}
+
 void datestamp(struct strbuf *out)
 {
 	time_t now;
diff --git a/date.h b/date.h
index bbd6a6477b..5d4eaba0a9 100644
--- a/date.h
+++ b/date.h
@@ -50,10 +50,17 @@ const char *show_date(timestamp_t time, int timezone, const struct date_mode *mo
  *
  * When the "date_mode_type" is DATE_STRFTIME the "strftime_fmt"
  * member of "struct date_mode" will be a malloc()'d format string to
- * be used with strbuf_addftime().
+ * be used with strbuf_addftime(), in which case you'll need to call
+ * date_mode_release() later.
  */
 void parse_date_format(const char *format, struct date_mode *mode);
 
+/**
+ * Release a "struct date_mode", currently only required if
+ * parse_date_format() has parsed a "DATE_STRFTIME" format.
+ */
+void date_mode_release(struct date_mode *mode);
+
 void show_date_relative(timestamp_t time, struct strbuf *timebuf);
 int parse_date(const char *date, struct strbuf *out);
 int parse_date_basic(const char *date, timestamp_t *timestamp, int *offset);
diff --git a/ref-filter.c b/ref-filter.c
index 3399bde932..7838bd22b8 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -1276,6 +1276,7 @@ static void grab_date(const char *buf, struct atom_value *v, const char *atomnam
 		goto bad;
 	v->s = xstrdup(show_date(timestamp, tz, &date_mode));
 	v->value = timestamp;
+	date_mode_release(&date_mode);
 	return;
  bad:
 	v->s = xstrdup("");
diff --git a/t/helper/test-date.c b/t/helper/test-date.c
index 111071e1dd..45951b1df8 100644
--- a/t/helper/test-date.c
+++ b/t/helper/test-date.c
@@ -54,6 +54,8 @@ static void show_dates(const char **argv, const char *format)
 
 		printf("%s -> %s\n", *argv, show_date(t, tz, &mode));
 	}
+
+	date_mode_release(&mode);
 }
 
 static void parse_dates(const char **argv)
diff --git a/t/t0006-date.sh b/t/t0006-date.sh
index 794186961e..2490162071 100755
--- a/t/t0006-date.sh
+++ b/t/t0006-date.sh
@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='test date parsing and printing'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 # arbitrary reference time: 2009-08-30 19:20:00