diff --git a/changes/19974 b/changes/19974
new file mode 100644
index 000000000..5496143dd
--- /dev/null
+++ b/changes/19974
@@ -0,0 +1,5 @@
+  o Minor bugfixes (unit tests):
+    - Fix tolerances in unit tests for monotonic time comparisons between
+      nanoseconds and microseconds. Previously, we accepted a 10 us
+      difference only, which is not realistic on every platform's
+      clock_gettime(). Fixes bug 19974; bugfix on 0.2.9.1-alpha.
diff --git a/src/test/test_util.c b/src/test/test_util.c
index 7276c0cbf..fcda56456 100644
--- a/src/test/test_util.c
+++ b/src/test/test_util.c
@@ -5531,9 +5531,9 @@ test_util_monotonic_time(void *arg)
   tt_u64_op(msecc1, OP_GE, nsecc1 / 1000000);
   tt_u64_op(usecc1, OP_GE, nsecc1 / 1000);
   tt_u64_op(msec1, OP_LE, nsec1 / 1000000 + 1);
-  tt_u64_op(usec1, OP_LE, nsec1 / 1000 +10);
+  tt_u64_op(usec1, OP_LE, nsec1 / 1000 + 1000);
   tt_u64_op(msecc1, OP_LE, nsecc1 / 1000000 + 1);
-  tt_u64_op(usecc1, OP_LE, nsecc1 / 1000 + 10);
+  tt_u64_op(usecc1, OP_LE, nsecc1 / 1000 + 1000);
 
  done:
   ;