diff --git a/README.md b/README.md
index af7ab2cf..6c30c878 100644
--- a/README.md
+++ b/README.md
@@ -58,11 +58,11 @@ FROM alpine:3.11
 
 ADD https://dl.bintray.com/php-alpine/key/php-alpine.rsa.pub /etc/apk/keys/php-alpine.rsa.pub
 
-RUN apk --update add ca-certificates && \
+RUN apk --update-cache add ca-certificates && \
     echo "https://dl.bintray.com/php-alpine/v3.11/php-7.4" >> /etc/apk/repositories
 
 # install php and some extensions
-RUN apk add --update \
+RUN apk add --update-cache \
     php \
     php-bz2 \
     php-json \
diff --git a/images/Dockerfile b/images/Dockerfile
index cf9d8f24..701832bc 100644
--- a/images/Dockerfile
+++ b/images/Dockerfile
@@ -15,22 +15,22 @@ ARG ALPINE_VERSION
 ARG PHP_VERSION
 
 # ADD SDK AND BASIC TOOLS.
-RUN apk add --update alpine-sdk sudo git bash nano
+RUN apk add --update-cache alpine-sdk sudo git bash nano
 
 # trust this project public key to trust the packages.
 ADD https://dl.bintray.com/php-alpine/key/php-alpine.rsa.pub /etc/apk/keys/php-alpine.rsa.pub
 
 # make sure you can use HTTPS
-RUN apk --update add ca-certificates
+RUN apk --update-cache add ca-certificates
 
 # CONFIGURE ALPINE REPOSITORIES AND PHP BUILD DIR.
 RUN echo "http://dl-cdn.alpinelinux.org/alpine/v${ALPINE_VERSION}/main" > /etc/apk/repositories && \
     echo "http://dl-cdn.alpinelinux.org/alpine/v${ALPINE_VERSION}/community" >> /etc/apk/repositories && \
     echo "https://dl.bintray.com/php-alpine/v${ALPINE_VERSION}/php-${PHP_VERSION}" >> /etc/apk/repositories
 
-RUN apk add --update \
+RUN apk add --update-cache \
     php \
     php-mbstring
 
 # START WITH BASH.
-CMD ["/bin/bash"]
\ No newline at end of file
+CMD ["/bin/bash"]
diff --git a/sandbox/Dockerfile b/sandbox/Dockerfile
index cff52fed..908ab640 100644
--- a/sandbox/Dockerfile
+++ b/sandbox/Dockerfile
@@ -17,7 +17,7 @@ ARG APK_PACKAGER
 ARG APK_MAINTAINER
 
 # ADD SDK AND BASIC TOOLS.
-RUN apk add --update alpine-sdk sudo git bash nano
+RUN apk add --update-cache alpine-sdk sudo git bash nano
 
 # CONFIGURE ALPINE REPOSITORIES AND PHP BUILD DIR.
 RUN echo "http://dl-cdn.alpinelinux.org/alpine/v${ALPINE_VERSION}/main" > /etc/apk/repositories && \
@@ -65,4 +65,4 @@ ENTRYPOINT ["/bin/start.sh"]
 WORKDIR "/home/sandbox/php-${PHP_VERSION}"
 
 # START WITH BASH.
-CMD ["/bin/bash"]
\ No newline at end of file
+CMD ["/bin/bash"]