diff --git a/test/unit/util.c b/test/unit/util.c
index ef4a596..982a0ce 100644
--- a/test/unit/util.c
+++ b/test/unit/util.c
@@ -508,9 +508,18 @@ test_unit(void)
   TEST_CHECK(UTI_DoubleToNtp32(65536.0) == htonl(0xffffffff));
   TEST_CHECK(UTI_DoubleToNtp32(65537.0) == htonl(0xffffffff));
 
+  TEST_CHECK(UTI_DoubleToNtp32f28(-1.0) == htonl(0));
+  TEST_CHECK(UTI_DoubleToNtp32f28(0.0) == htonl(0));
+  TEST_CHECK(UTI_DoubleToNtp32f28(1e-9) == htonl(1));
+  TEST_CHECK(UTI_DoubleToNtp32f28(4e-9) == htonl(2));
+  TEST_CHECK(UTI_DoubleToNtp32f28(8.0) == htonl(0x80000000));
+  TEST_CHECK(UTI_DoubleToNtp32f28(16.0) == htonl(0xffffffff));
+  TEST_CHECK(UTI_DoubleToNtp32f28(16.1) == htonl(0xffffffff));
+
   for (i = 0; i < 100000; i++) {
     UTI_GetRandomBytes(&ntp32_ts, sizeof (ntp32_ts));
     TEST_CHECK(UTI_DoubleToNtp32(UTI_Ntp32ToDouble(ntp32_ts)) == ntp32_ts);
+    TEST_CHECK(UTI_DoubleToNtp32f28(UTI_Ntp32f28ToDouble(ntp32_ts)) == ntp32_ts);
   }
 
   ts.tv_nsec = 0;
diff --git a/util.c b/util.c
index 82f8de7..1f66480 100644
--- a/util.c
+++ b/util.c
@@ -637,6 +637,37 @@ UTI_DoubleToNtp32(double x)
 
 /* ================================================== */
 
+double
+UTI_Ntp32f28ToDouble(NTP_int32 x)
+{
+  return ntohl(x) / (double)(1U << 28);
+}
+
+/* ================================================== */
+
+NTP_int32
+UTI_DoubleToNtp32f28(double x)
+{
+  NTP_int32 r;
+
+  if (x >= 4294967295.0 / (1U << 28)) {
+    r = 0xffffffff;
+  } else if (x <= 0.0) {
+    r = 0;
+  } else {
+    x *= 1U << 28;
+    r = x;
+
+    /* Round up */
+    if (r < x)
+      r++;
+  }
+
+  return htonl(r);
+}
+
+/* ================================================== */
+
 void
 UTI_ZeroNtp64(NTP_int64 *ts)
 {
diff --git a/util.h b/util.h
index 434a9b4..f6bf7b9 100644
--- a/util.h
+++ b/util.h
@@ -133,6 +133,9 @@ extern void UTI_GetNtp64Fuzz(NTP_int64 *ts, int precision);
 extern double UTI_Ntp32ToDouble(NTP_int32 x);
 extern NTP_int32 UTI_DoubleToNtp32(double x);
 
+extern double UTI_Ntp32f28ToDouble(NTP_int32 x);
+extern NTP_int32 UTI_DoubleToNtp32f28(double x);
+
 /* Zero an NTP timestamp */
 extern void UTI_ZeroNtp64(NTP_int64 *ts);