diff --git a/docker-builders/Swiftshader.Dockerfile b/docker-builders/Swiftshader.Dockerfile
index 1e492beac..1a6e9ba37 100644
--- a/docker-builders/Swiftshader.Dockerfile
+++ b/docker-builders/Swiftshader.Dockerfile
@@ -29,6 +29,6 @@ RUN apt-get install -y libxext-dev
 # Run swiftshader via env VK_ICD_FILENAMES=/swiftshader/vk_swiftshader_icd.json
 RUN git clone https://github.com/google/swiftshader swiftshader-build
 RUN CC="/usr/bin/gcc-8" CXX="/usr/bin/g++-8" cmake swiftshader-build/. -Bswiftshader-build/build/
-RUN cmake --build swiftshader-build/build/. --parallel 12
+RUN cmake --build swiftshader-build/build/. --parallel
 RUN cp -r swiftshader-build/build/Linux/ swiftshader/
 
diff --git a/docker-builders/VulkanSDK.Dockerfile b/docker-builders/VulkanSDK.Dockerfile
index cdece9e59..ce42da579 100644
--- a/docker-builders/VulkanSDK.Dockerfile
+++ b/docker-builders/VulkanSDK.Dockerfile
@@ -29,7 +29,7 @@ RUN wget -O - https://apt.kitware.com/keys/kitware-archive-latest.asc 2>/dev/nul
 RUN apt-add-repository 'deb https://apt.kitware.com/ubuntu/ bionic main'
 # Adding security repo to add cmake dependency on libssl 1.0
 RUN echo "deb http://security.ubuntu.com/ubuntu bionic-security main" | tee -a /etc/apt/sources.list.d/bionic.list
-RUN apt-get update
+RUN apt-get update --fix-missing -y
 RUN apt-get upgrade -y
 
 # Install build dependencies