diff --git a/js/src/devtools/automation/autospider.sh b/js/src/devtools/automation/autospider.sh
index 1f36204cd444..57d39da4c1a2 100755
--- a/js/src/devtools/automation/autospider.sh
+++ b/js/src/devtools/automation/autospider.sh
@@ -105,10 +105,14 @@ elif [ "$OSTYPE" = "linux-gnu" ]; then
     fi
   fi
 elif [ "$OSTYPE" = "msys" ]; then
-  USE_64BIT=false
-  if [ "$platform" = "win64" ]; then
-      USE_64BIT=true
-  fi
+  case "$platform" in
+  win64*)
+    USE_64BIT=true
+    ;;
+  *)
+    USE_64BIT=false
+    ;;
+  esac
   MAKE=${MAKE:-mozmake}
   source "$ABSDIR/winbuildenv.sh"
 fi