Changes in the ground-state electron momentum density of tetra-hydrofuran clathrate hydrate are studied in a temperature range between 93 and 275 K by means of X-ray Compton scattering. At temperatures above 253 K, large rather unexpected differences from the Compton profiles of ice are observed. Configurational enthalpies are extracted and exhibit a rapid rise above 253 K, whereas a constant configurational heat capacity of 0.23 +/- 0.07 J g(-1) K(-1) is found below 253 K. Density functional theory calculations suggest that this abomalous behavior originates from the structural change of the hydrate, however, no indication was found for the formation of hydrogen bonds between tetrahydro-furan and water molecules.