diff --git a/Makefile.am b/Makefile.am
index cdf82ab4..7ee613ba 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1194,6 +1194,7 @@ internal_tests = 				\
 
 shared_tests =					\
 	config-parser.test			\
+	timespec.test				\
 	string.test					\
 	vertex-clip.test			\
 	zuctest
@@ -1307,6 +1308,15 @@ config_parser_test_CFLAGS =			\
 	$(AM_CFLAGS)				\
 	-I$(top_srcdir)/tools/zunitc/inc
 
+timespec_test_SOURCES = tests/timespec-test.c
+timespec_test_LDADD =	\
+	libshared.la		\
+	libzunitc.la		\
+	libzunitcmain.la
+timespec_test_CFLAGS =			\
+	$(AM_CFLAGS)				\
+	-I$(top_srcdir)/tools/zunitc/inc
+
 string_test_SOURCES = \
 	tests/string-test.c \
 	shared/string-helpers.h
diff --git a/shared/timespec-util.h b/shared/timespec-util.h
index edd4ec14..a1d6881b 100644
--- a/shared/timespec-util.h
+++ b/shared/timespec-util.h
@@ -49,6 +49,27 @@ timespec_sub(struct timespec *r,
 	}
 }
 
+/* Add a nanosecond value to a timespec
+ *
+ * \param r[out] result: a + b
+ * \param a[in] base operand as timespec
+ * \param b[in] operand in nanoseconds
+ */
+static inline void
+timespec_add_nsec(struct timespec *r, const struct timespec *a, int64_t b)
+{
+	r->tv_sec = a->tv_sec + (b / NSEC_PER_SEC);
+	r->tv_nsec = a->tv_nsec + (b % NSEC_PER_SEC);
+
+	if (r->tv_nsec >= NSEC_PER_SEC) {
+		r->tv_sec++;
+		r->tv_nsec -= NSEC_PER_SEC;
+	} else if (r->tv_nsec < 0) {
+		r->tv_sec--;
+		r->tv_nsec += NSEC_PER_SEC;
+	}
+}
+
 /* Convert timespec to nanoseconds
  *
  * \param a timespec
diff --git a/tests/timespec-test.c b/tests/timespec-test.c
new file mode 100644
index 00000000..91d53f73
--- /dev/null
+++ b/tests/timespec-test.c
@@ -0,0 +1,124 @@
+/*
+ * Copyright © 2016 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+#include <errno.h>
+#include <unistd.h>
+
+#include "timespec-util.h"
+
+#include "shared/helpers.h"
+#include "zunitc/zunitc.h"
+
+ZUC_TEST(timespec_test, timespec_sub)
+{
+	struct timespec a, b, r;
+
+	a.tv_sec = 1;
+	a.tv_nsec = 1;
+	b.tv_sec = 0;
+	b.tv_nsec = 2;
+	timespec_sub(&r, &a, &b);
+	ZUC_ASSERT_EQ(r.tv_sec, 0);
+	ZUC_ASSERT_EQ(r.tv_nsec, NSEC_PER_SEC - 1);
+}
+
+ZUC_TEST(timespec_test, timespec_to_nsec)
+{
+	struct timespec a;
+
+	a.tv_sec = 4;
+	a.tv_nsec = 4;
+	ZUC_ASSERT_EQ(timespec_to_nsec(&a), (NSEC_PER_SEC * 4ULL) + 4);
+}
+
+ZUC_TEST(timespec_test, millihz_to_nsec)
+{
+	ZUC_ASSERT_EQ(millihz_to_nsec(60000), 16666666);
+}
+
+ZUC_TEST(timespec_test, timespec_add_nsec)
+{
+	struct timespec a, r;
+
+	a.tv_sec = 0;
+	a.tv_nsec = NSEC_PER_SEC - 1;
+	timespec_add_nsec(&r, &a, 1);
+	ZUC_ASSERT_EQ(1, r.tv_sec);
+	ZUC_ASSERT_EQ(0, r.tv_nsec);
+
+	timespec_add_nsec(&r, &a, 2);
+	ZUC_ASSERT_EQ(1, r.tv_sec);
+	ZUC_ASSERT_EQ(1, r.tv_nsec);
+
+	timespec_add_nsec(&r, &a, (NSEC_PER_SEC * 2ULL));
+	ZUC_ASSERT_EQ(2, r.tv_sec);
+	ZUC_ASSERT_EQ(NSEC_PER_SEC - 1, r.tv_nsec);
+
+	timespec_add_nsec(&r, &a, (NSEC_PER_SEC * 2ULL) + 2);
+	ZUC_ASSERT_EQ(r.tv_sec, 3);
+	ZUC_ASSERT_EQ(r.tv_nsec, 1);
+
+	a.tv_sec = 1;
+	a.tv_nsec = 1;
+	timespec_add_nsec(&r, &a, -2);
+	ZUC_ASSERT_EQ(r.tv_sec, 0);
+	ZUC_ASSERT_EQ(r.tv_nsec, NSEC_PER_SEC - 1);
+
+	a.tv_nsec = 0;
+	timespec_add_nsec(&r, &a, -NSEC_PER_SEC);
+	ZUC_ASSERT_EQ(0, r.tv_sec);
+	ZUC_ASSERT_EQ(0, r.tv_nsec);
+
+	a.tv_nsec = 0;
+	timespec_add_nsec(&r, &a, -NSEC_PER_SEC + 1);
+	ZUC_ASSERT_EQ(0, r.tv_sec);
+	ZUC_ASSERT_EQ(1, r.tv_nsec);
+
+	a.tv_nsec = 50;
+	timespec_add_nsec(&r, &a, (-NSEC_PER_SEC * 10ULL));
+	ZUC_ASSERT_EQ(-9, r.tv_sec);
+	ZUC_ASSERT_EQ(50, r.tv_nsec);
+
+	r.tv_sec = 4;
+	r.tv_nsec = 0;
+	timespec_add_nsec(&r, &r, NSEC_PER_SEC + 10ULL);
+	ZUC_ASSERT_EQ(5, r.tv_sec);
+	ZUC_ASSERT_EQ(10, r.tv_nsec);
+
+	timespec_add_nsec(&r, &r, (NSEC_PER_SEC * 3ULL) - 9ULL);
+	ZUC_ASSERT_EQ(8, r.tv_sec);
+	ZUC_ASSERT_EQ(1, r.tv_nsec);
+
+	timespec_add_nsec(&r, &r, (NSEC_PER_SEC * 7ULL) + (NSEC_PER_SEC - 1ULL));
+	ZUC_ASSERT_EQ(16, r.tv_sec);
+	ZUC_ASSERT_EQ(0, r.tv_nsec);
+}