text/x-handlebars MIME Type not supported in sprocket

[imechemi]

Hi, after upgrading rails from 4.2.4 to 4.2.5.1, the sprocket gem also got updated from 3.4.0 to 3.5.2. And my application broke while rendering .hamlbars file from assets.

The backtrace from app ends at this line from sprocket when the text/x-handlebars mime type is not found.

Below are the MIME types I found using puts from sprockets at that line and it doesn't have "text/x-handlebars" in the list.

{"application/javascript"=>{:extensions=>[".js"], :charset=>#<Method: Module(Sprockets::EncodingUtils)#detect_unicode>}, 
"application/json"=>{:extensions=>[".json"], :charset=>#<Method: Module(Sprockets::EncodingUtils)#detect_unicode>}, 
"application/xml"=>{:extensions=>[".xml"]}, 
"text/css"=>{:extensions=>[".css"], :charset=>#<Method: Module(Sprockets::EncodingUtils)#detect_css>}, 
"text/html"=>{:extensions=>[".html", ".htm"], :charset=>#<Method: Module(Sprockets::EncodingUtils)#detect_html>}, 
"text/plain"=>{:extensions=>[".txt", ".text"], :charset=>#<Method: Module(Sprockets::EncodingUtils)#detect>}, 
"text/yaml"=>{:extensions=>[".yml", ".yaml"], :charset=>#<Method: Module(Sprockets::EncodingUtils)#detect_unicode>}, 
"image/x-icon"=>{:extensions=>[".ico"]}, 
"image/bmp"=>{:extensions=>[".bmp"]}, 
"image/gif"=>{:extensions=>[".gif"]}, 
"image/webp"=>{:extensions=>[".webp"]}, 
"image/png"=>{:extensions=>[".png"]}, 
"image/jpeg"=>{:extensions=>[".jpg", ".jpeg"]}, 
"image/tiff"=>{:extensions=>[".tiff", ".tif"]}, 
"image/svg+xml"=>{:extensions=>[".svg"]}, 
"video/webm"=>{:extensions=>[".webm"]},
"audio/basic"=>{:extensions=>[".snd", ".au"]}, 
"audio/aiff"=>{:extensions=>[".aiff"]}, 
"audio/mpeg"=>{:extensions=>[".mp3", ".mp2", ".m2a", ".m3a"]}, 
"application/ogg"=>{:extensions=>[".ogx"]}, 
"audio/midi"=>{:extensions=>[".midi", ".mid"]}, 
"video/avi"=>{:extensions=>[".avi"]}, 
"audio/wave"=>{:extensions=>[".wav", ".wave"]}, 
"video/mp4"=>{:extensions=>[".mp4", ".m4v"]}, 
"application/vnd.ms-fontobject"=>{:extensions=>[".eot"]}, 
"application/x-font-ttf"=>{:extensions=>[".ttf"]}, 
"application/font-woff"=>{:extensions=>[".woff"]}}

I am not sure if this is handlebars_assets or sprocket issue.