My https version is indexed even though the canonical tag references the http://. Is this a major concern?

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Bryan Greenway: Hi, I'm seeing the https:// version of some of our pages indexed vs. http://, even though the canonical tag references the ;http://.
  
  Is this a major concern? if so what could we do to give a stronger hint to Google not to index the secure versions of our pages?
  
  Thanks in advance
• 
  Dave Elliott: Out of interest why would you not want the secure versions of pages being indexed? Is it certain pages (like say a blog/about us section) you are not wanting to be indexed or the entire site.
  
  sorry, no help, but i am intrigued!
• 
  Bryan Greenway: No specific reason other than no need to index both (I assume) secure and non secure. i.e. the same content at two different urls. ;
• 
  Mike Ramirez: Have you tried adding a noindex tag to your https pages? ;
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  Bryan Greenway: Well, again and pardon if I'm not following you, they're the same pages secure or not, so not sure how that tag would work. i.e. https://www.domain.com vs.http://www.domain.com technically the same page so the tag(s) would be the same as well.
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  Tony McCreath: I think they recomend not mixing canonical with noindex. can send mixed signals. Are you sure your canonical always points to the http version?
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  Chris Smit: If you set the httpS to no-index (no-follow), why would you have them in the first place?