openssl and OCSP

I am trying to check the revocation of certificates in a script but I get the following error:

unable to load certificate
140735258465104:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:703:Expecting: TRUSTED CERTIFICATE

Here the steps (using www.google.com as an example)

1. 
   

   fetch the certificate

   
   

   
   echo 'Q' | openssl s_client -connect www.google.com:443 > google.crt
   
   



2. 
   

   extract the URI of the issuer

   
   

   
   openssl x509 -in google.crt -text -noout | grep 'CA Issuers' | sed -e "s/^.*CA Issuers - URI://
   
   

   
   

   this gives http://pki.google.com/GIAG2.crt

   
   


3. 
   

   fetch the issuer certificate

   
   

   
   curl --silent http://pki.google.com/GIAG2.crt > issuer.crt
   
   



4. 
   

   extract the OCSP URI

   
   

   
   openssl x509 -in google.crt -ocsp_uri -noout
   
   

   
   

   this gives http://clients1.google.com/ocsp

   
   

And now the final step:

$ openssl ocsp -no_nonce -issuer issuer.crt -cert google.crt -url http://clients1.google.com/ocsp
unable to load certificate
140735258465104:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:703:Expecting: TRUSTED CERTIFICATE

What am I doing wrong?