diff --git a/Dockerfile-slim b/Dockerfile-slim
index 505e00acc..450d33dd1 100644
--- a/Dockerfile-slim
+++ b/Dockerfile-slim
@@ -6,7 +6,7 @@ ENV SITESPEED_IO_BROWSERTIME__BROWSER firefox
 ENV SITESPEED_IO_BROWSERTIME__VISUAL_METRICS false
 ENV SITESPEED_IO_BROWSERTIME__HEADLESS true
 
-ENV FIREFOX_VERSION 76.0
+ENV FIREFOX_VERSION 78.0
 
 ENV PATH="/usr/local/bin:${PATH}"