Author and Wharton Professor Jeremy Siegel says a bubble is forming in the bond market, and that those who continue to rush into bonds are making the same kind of mistake investors made back during the technology bubble of the late 1990s. Siegel tells CNBC that investors are showing “tremendous risk aversion” of the order they showed in the weeks following Lehman Brothers’ collapse, even though things aren’t nearly as bad as they were back then.

Siegel also recently co-authored with Jeremy Schwartz a Wall Street Journal op-ed piece on “The Great American Bond Bubble,” which can be viewed here.