diff --git a/Tools/scripts/build_binaries.sh b/Tools/scripts/build_binaries.sh
index b721b77dad..991417b006 100755
--- a/Tools/scripts/build_binaries.sh
+++ b/Tools/scripts/build_binaries.sh
@@ -331,9 +331,9 @@ build_arducopter() {
                 error_count=$((error_count+1))
                 continue
             }
-            extension = ""
+            extension=""
             if [ -f $BUILDROOT/$b/bin/arducopter${framesuffix}.px4 ]; then
-                exension = ".px4"
+                extension=".px4"
             fi
             copyit $BUILDROOT/$b/bin/arducopter${framesuffix}${extension} $ddir $tag "ArduCopter"
             touch $binaries/Copter/$tag