diff --git a/Dockerfile.glibc b/Dockerfile.glibc
index 47a8998..fd0a1f5 100644
--- a/Dockerfile.glibc
+++ b/Dockerfile.glibc
@@ -1,4 +1,4 @@
-FROM debian AS build
+FROM debian:10 AS build
 
 ARG PCRE_VERSION="8.43"
 ARG PCRE_CHECKSUM="0b8e7465dc5e98c757cc3650a20a7843ee4c3edf50aaf60bb33fd879690d2c73"
diff --git a/Dockerfile.musl b/Dockerfile.musl
index f71a8f9..87d34be 100644
--- a/Dockerfile.musl
+++ b/Dockerfile.musl
@@ -1,4 +1,4 @@
-FROM alpine AS build
+FROM alpine:3 AS build
 
 ARG PCRE_VERSION="8.43"
 ARG PCRE_CHECKSUM="0b8e7465dc5e98c757cc3650a20a7843ee4c3edf50aaf60bb33fd879690d2c73"