diff --git a/changes/bug19968 b/changes/bug19968
new file mode 100644
index 000000000..b285706e7
--- /dev/null
+++ b/changes/bug19968
@@ -0,0 +1,11 @@
+  o Minor bugfixes (relay):
+    - Do not try to parallelize workers more than 16x without the
+      user explicitly configuring us to do so, even if we do detect more than
+      16 CPU cores. Fixes bug 19968; bugfix on
+      0.2.3.1-alpha.
+
+
+  o Minor bugfixes (testing):
+    - Avoid a unit test failure on systems with over 16 detectable
+      CPU cores. Fixes bug 19968; bugfix on
+      0.2.3.1-alpha.
diff --git a/src/common/compat.c b/src/common/compat.c
index 3fde2b308..4f2f9778f 100644
--- a/src/common/compat.c
+++ b/src/common/compat.c
@@ -2818,6 +2818,7 @@ compute_num_cpus(void)
                  "will not autodetect any more than %d, though.  If you "
                  "want to configure more, set NumCPUs in your torrc",
                  num_cpus, MAX_DETECTABLE_CPUS);
+      num_cpus = MAX_DETECTABLE_CPUS;
       /* LCOV_EXCL_STOP */
     }
   }