diff --git a/tools/build-pr/report b/tools/build-pr/report
index 9f34d1fe1c..518ee2a797 100755
--- a/tools/build-pr/report
+++ b/tools/build-pr/report
@@ -31,6 +31,8 @@ fi
 
 get_pr_info
 
+if [[ "$BUILDPR" = "0" ]]; then exit; fi
+
 text="The build has ${AGENT_JOBSTATUS,,}.  (${SHA1:0:8})"; more_text=""
 post_status "$state" "$text"
 delete_comment
diff --git a/tools/build-pr/shared.sh b/tools/build-pr/shared.sh
index 4af8b63aba..b098b5680d 100644
--- a/tools/build-pr/shared.sh
+++ b/tools/build-pr/shared.sh
@@ -5,7 +5,12 @@ set -e
 
 cd "$BASEDIR"
 
+# For private builds: <user>/<repo>/<branch>
+privatebuildrx="([^a-zA-Z0-9][^a-zA-Z0-9-]*)"
+privatebuildrx+="/([a-zA-Z0-9+-]+)/([a-zA-Z0-9/+-]+)"
+
 if [[ "$BUILDPR" = "" ]]; then :
+elif [[ "$BUILDPR" =~ $privatebuildrx ]]; then :
 elif [[ "$BUILDPR" = *[^0-9]* ]]; then
   echo "ERROR: \$BUILDPR should be a number, got: \"$BUILDPR\"" 1>&2
   exit 1
@@ -21,17 +26,19 @@ _get_T() {
 
 declare -A api_cache
 api() {
+  local repo="Azure/mmlspark"
+  if [[ "$1" = "-r" ]]; then repo="$2"; shift 2; fi
   local call="$1"; shift
   local curlargs=() x use_cache=1 json=""
   while (($# > 0)); do
     x="$1"; shift
-    if [[ "x$x" = "x-" ]]; then break; else use_cache=0; curlargs+=("$x"); fi;
+    if [[ "$x" = "-" ]]; then break; else use_cache=0; curlargs+=("$x"); fi;
   done
-  if ((use_cache)); then json="${api_cache["${call} ${curlargs[*]}"]}"; fi
+  if ((use_cache)); then json="${api_cache["${repo} ${call} ${curlargs[*]}"]}"; fi
   if [[ -z "$json" ]]; then
     _get_T
     json="$(curl --silent --show-error -H "AUTHORIZATION: bearer ${T#*:}" \
-                 "https://api.github.com/repos/Azure/mmlspark/$call" \
+                 "https://api.github.com/repos/$repo/$call" \
                  "${curlargs[@]}")"
     if ((use_cache)); then api_cache["${call} ${curlargs[*]}"]="$json"; fi
   fi
@@ -48,18 +55,27 @@ GURL="" SHA1="" REPO="" REF=""
 
 get_pr_info() {
   if [[ "$SHA1" != "" ]]; then return; fi
-  SHA1="$(api "pulls/$BUILDPR" - '.head.sha // empty')"
-  REPO="$(api "pulls/$BUILDPR" - '.head.repo.full_name // empty')"
-  REF="$( api "pulls/$BUILDPR" - '.head.ref // empty')"
-  GURL="$(api "pulls/$BUILDPR" - '.html_url // empty')"
-  if [[ -z "$SHA1" ]]; then failwith "no such PR: $BUILDPR"; fi
-  if [[ "$(api "pulls/$BUILDPR" - '.state')" != "open" ]]; then
-    failwith "PR#$BUILDPR is not open"
+  if [[ "$BUILDPR" = */*/* ]]; then # private builds
+    REPO="${BUILDPR%%/*}"; BUILDPR="${BUILDPR#*/}"; REPO="$REPO/${BUILDPR%%/*}"
+    REF="${BUILDPR#*/}"; BUILDPR="0"
+    GURL="https://github.com/$REPO/tree/$REF"
+    SHA1="$(api -r "$REPO" "git/refs/heads/$REF" - '.object.sha // empty')"
+    if [[ -z "$SHA1" ]]; then failwith "no such repo/ref: $REPO/$REF"; fi
+  else # plain pr builds
+    if [[ "$(api "pulls/$BUILDPR" - '.state')" != "open" ]]; then
+      failwith "PR#$BUILDPR is not open"
+    fi
+    SHA1="$(api "pulls/$BUILDPR" - '.head.sha // empty')"
+    if [[ -z "$SHA1" ]]; then failwith "no such PR: $BUILDPR"; fi
+    REPO="$(api "pulls/$BUILDPR" - '.head.repo.full_name // empty')"
+    REF="$( api "pulls/$BUILDPR" - '.head.ref // empty')"
+    GURL="$(api "pulls/$BUILDPR" - '.html_url // empty')"
   fi
 }
 
 # post a status, only if we're running all tests
 post_status() { # state text
+  if [[ "$BUILDPR" = "0" ]]; then return; fi
   if [[ "$TESTS" != "all" ]]; then return; fi
   local status='"context":"build-pr","state":"'"$1"'","target_url":"'"$VURL"'"'
   api "statuses/$SHA1" -d '{'"$status"',"description":'"$(jsonq "$2")"'}' > /dev/null
@@ -67,6 +83,7 @@ post_status() { # state text
 
 # post a comment with the given text and link to the build; remember its id
 post_comment() { # text [more-text...]
+  if [[ "$BUILDPR" = "0" ]]; then return; fi
   local text="[$1]($VURL)"; shift; local more_text="$*"
   if [[ "$more_text" != "" ]]; then text+=$'\n\n'"$more_text"; fi
   api "issues/$BUILDPR/comments" -d '{"body":'"$(jsonq "$text")"'}' - '.id' \
@@ -75,6 +92,7 @@ post_comment() { # text [more-text...]
 
 # delete the last posted comment
 delete_comment() {
+  if [[ "$BUILDPR" = "0" ]]; then return; fi
   if [[ ! -r "$PRDIR/comment-id" ]]; then return; fi
   api "issues/comments/$(< "$PRDIR/comment-id")" -X DELETE
 }