diff --git a/bin/init/qsp-units.heta b/bin/init/qsp-units.heta
index c1e86437..af7f84d2 100644
--- a/bin/init/qsp-units.heta
+++ b/bin/init/qsp-units.heta
@@ -136,7 +136,7 @@ um #defineUnit {
     units: [ { kind: metre, multiplier: 1e-6 } ]
 };
 mm #defineUnit {
-    units: [ { kind: metre, multiplier: 1e-13 } ]
+    units: [ { kind: metre, multiplier: 1e-3 } ]
 };
 cm #defineUnit {
     units: [ { kind: metre, multiplier: 1e-2 } ]