diff --git a/tools/docker/Dockerfile b/tools/docker/Dockerfile
index 5d3bd4e24ab..9d10de5b892 100644
--- a/tools/docker/Dockerfile
+++ b/tools/docker/Dockerfile
@@ -315,4 +315,4 @@ RUN /bin/echo -e "\nx86 = i386" >> ~/.buildman;
 
 # Add mkbootimg tool
 RUN git clone https://android.googlesource.com/platform/system/tools/mkbootimg /home/uboot/mkbootimg
-ENV PYTHONPATH "${PYTHONPATH}:/home/uboot/mkbootimg"
+ENV PYTHONPATH="${PYTHONPATH}:/home/uboot/mkbootimg"