--- a/browser/config/mozconfigs/win32/common-opt
+++ b/browser/config/mozconfigs/win32/common-opt
@@ -1,23 +1,23 @@
 # This file is sourced by the nightly, beta, and release mozconfigs.
 
 . "$topsrcdir/browser/config/mozconfigs/common"
 
 ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
 ac_add_options --enable-jemalloc
 
 if [ -f /c/builds/gapi.data ]; then
-  _gapi_keyfile=/c/builds/gapi.data
+  _gapi_keyfile=c:/builds/gapi.data
 else
-  _gapi_keyfile=/e/builds/gapi.data
+  _gapi_keyfile=e:/builds/gapi.data
 fi
 ac_add_options --with-google-api-keyfile=${_gapi_keyfile}
 
-ac_add_options --with-mozilla-api-keyfile=/c/builds/mozilla-desktop-geoloc-api.key
+ac_add_options --with-mozilla-api-keyfile=c:/builds/mozilla-desktop-geoloc-api.key
 
 # Needed to enable breakpad in application.ini
 export MOZILLA_OFFICIAL=1
 
 export MOZ_TELEMETRY_REPORTING=1
 
 . $topsrcdir/build/win32/mozconfig.vs-latest
 

--- a/browser/config/mozconfigs/win64/common-opt
+++ b/browser/config/mozconfigs/win64/common-opt
@@ -1,22 +1,22 @@
 # This file is sourced by the nightly, beta, and release mozconfigs.
 
 . "$topsrcdir/browser/config/mozconfigs/common"
 
 ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
 ac_add_options --enable-jemalloc
 if [ -f /c/builds/gapi.data ]; then
-  _gapi_keyfile=/c/builds/gapi.data
+  _gapi_keyfile=c:/builds/gapi.data
 else
-  _gapi_keyfile=/e/builds/gapi.data
+  _gapi_keyfile=e:/builds/gapi.data
 fi
 ac_add_options --with-google-api-keyfile=${_gapi_keyfile}
 
-ac_add_options --with-mozilla-api-keyfile=/c/builds/mozilla-desktop-geoloc-api.key
+ac_add_options --with-mozilla-api-keyfile=c:/builds/mozilla-desktop-geoloc-api.key
 
 # Needed to enable breakpad in application.ini
 export MOZILLA_OFFICIAL=1
 
 export MOZ_TELEMETRY_REPORTING=1
 
 . $topsrcdir/build/win64/mozconfig.vs-latest