2017-09-18 r73296 does not compile rmarkdown correctly

[sammo3182]

I just installed the 2017-09-18 r73296 development version of R and tried to compile an existing .rmd file. There was only one line of command, processing file: XXX.Rmd shown in the R Markdown terminal, and nothing was updated. When I switched back to 3.4.1, The file performs correctly. Here's my sessionInfo()

R Under development (unstable) (2017-09-17 r73296)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)

Matrix products: default

locale:
[1] LC_COLLATE=English_United States.1252 
[2] LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] stats     graphics  grDevices
[4] utils     datasets  methods  
[7] base     

loaded via a namespace (and not attached):
[1] compiler_3.5.0 tools_3.5.0   
[3] yaml_2.1.14