diff --git a/script/start-local-collaboration b/script/start-local-collaboration
index 8906593509..4748ca0474 100755
--- a/script/start-local-collaboration
+++ b/script/start-local-collaboration
@@ -26,7 +26,7 @@ fi
 
 # Make each Zed instance take up half of the screen.
 resolution_line=$(system_profiler SPDisplaysDataType | grep Resolution | head -n1)
-screen_size=($(echo $resolution_line | egrep -o '[0-9]+'))
+screen_size=($(echo $resolution_line | egrep -o '\s*(\d+)\s*x\s*(\d+).*)' | egrep -o '[0-9]+'))
 scale_factor=1
 if [[ $resolution_line =~ Retina ]]; then scale_factor=2; fi
 width=$(expr ${screen_size[0]} / 2 / $scale_factor)
@@ -36,6 +36,17 @@ y=0
 position_1=0,${y}
 position_2=${width},${y}
 
+# Uncomment the following for debugging purposes.
+# echo "Resolution line: $resolution_line"
+# echo "Screen size: $screen_size"
+# echo "Screen size 0: ${screen_size[0]}"
+# echo "Screen size 1: ${screen_size[1]}"
+# echo "Scale factor: $scale_factor"
+# echo "Width: $width"
+# echo "Height: $height"
+# echo "Position 1: $position_1"
+# echo "Position 2: $position_2"
+
 # Authenticate using the collab server's admin secret.
 export ZED_STATELESS=1
 export ZED_ADMIN_API_TOKEN=secret