diff --git a/src/auxiliary_particle_filter.m b/src/auxiliary_particle_filter.m
index 905a569d26ca00bbf796f856c2e2a1050430bf8d..737d1a6da06ff0dc342d7275bbe7659af2b209f7 100644
--- a/src/auxiliary_particle_filter.m
+++ b/src/auxiliary_particle_filter.m
@@ -134,6 +134,7 @@ for t=1:sample_size
     if (ParticleOptions.resampling.status.generic && neff(weights)<ParticleOptions.resampling.threshold*sample_size) || ParticleOptions.resampling.status.systematic
         if pruning
             temp = resample([StateVectors' StateVectors_'],weights',ParticleOptions);
+            number_of_state_variables=size(StateVectors,1);
             StateVectors = temp(:,1:number_of_state_variables)';
             StateVectors_ = temp(:,number_of_state_variables+1:2*number_of_state_variables)';
         else