diff --git a/include/villas/hooks/pmu.hpp b/include/villas/hooks/pmu.hpp
index 27555c462..b3c1d5ecf 100644
--- a/include/villas/hooks/pmu.hpp
+++ b/include/villas/hooks/pmu.hpp
@@ -58,8 +58,8 @@ class PmuHook : public MultiSignalHook {
   double frequencyOffset;
   double rocofOffset;
 
-  Phasor estimatePhasor(dsp::CosineWindow<double> *window,
-                        const Phasor &lastPhasor);
+  virtual Phasor estimatePhasor(dsp::CosineWindow<double> *window,
+                                const Phasor &lastPhasor);
 
 public:
   PmuHook(Path *p, Node *n, int fl, int prio, bool en = true);