Abstract: In the path integral quantization of Yang-Mills theory, integer topological sectors follow only when Euclidean time is taken to infinity. This implies that the spacetime volume must be taken to infinity before interfering among the sectors. On the other hand, in canonical quantization, the standard theta-vacua are not properly normalizable without further ado. We revisit the well-known analogy with a point particle on a circle. It is sometimes argued that continuous energy bands corresponding to Bloch states exist for this problem. We show however that the states in these bands exhibit an inconsistent time evolution, unless narrowing the energy band to just one allowed state. From either perspective one can understand why no CP violation is seen in the strong interactions.