diff --git a/src/system/bsdl_check.cpp b/src/system/bsdl_check.cpp
index 16d07b1..9d88599 100644
--- a/src/system/bsdl_check.cpp
+++ b/src/system/bsdl_check.cpp
@@ -104,7 +104,10 @@ std::vector<Anomaly> check_pin_specs(System *sys)
             out.push_back(std::move(a));
         }
 
-        if (ins >= 1 && drivers == 0) {
+        // Only conclude "undriven" when the whole net is modelled (every pin
+        // has a known direction). Otherwise the driver may sit on an
+        // un-modelled part (direction Unknown) and we must not flag it.
+        if (ins >= 1 && drivers == 0 && known == (int)pins.size()) {
             Anomaly a;
             a.kind = AnomalyKind::UndrivenNet;
             a.module = mod;