We present refined diffuse neutron scattering measurements performed in the long-range-ordered phase of potassium thiocyanate ($T < T_c$). The analysis of the data yields that the diffuse scattering is due to the presence of order-parameter fluctuations that appear as a precursor to the order-disorder phase transition. The diffuse intensity increases when approaching $T_c$ from below, whereas the width remains constant in the whole long-range-ordered phase. Molecular-dynamics simulations indicate that the size of the precursor clusters is stabilized by the order-parameter–strain interactions.