diff --git a/boefjes/Dockerfile b/boefjes/Dockerfile
index c0a75319776..86c2df85133 100644
--- a/boefjes/Dockerfile
+++ b/boefjes/Dockerfile
@@ -6,8 +6,8 @@ ARG USER_GID=1000
 
 ENTRYPOINT ["/app/boefjes/entrypoint.sh"]
 
-RUN groupadd --gid $USER_GID nonroot
-RUN adduser --disabled-password --gecos '' --uid $USER_UID --gid $USER_GID nonroot
+RUN groupadd --gid "$USER_GID" nonroot
+RUN adduser --disabled-password --gecos '' --uid "$USER_UID" --gid "$USER_GID" nonroot
 
 WORKDIR /app/boefjes
 ENV PATH=/home/nonroot/.local/bin:${PATH}
diff --git a/bytes/Dockerfile b/bytes/Dockerfile
index cca6359d97d..7b159a92a62 100644
--- a/bytes/Dockerfile
+++ b/bytes/Dockerfile
@@ -8,8 +8,8 @@ ARG USER_GID=1000
 
 ENTRYPOINT ["/app/bytes/entrypoint.sh"]
 
-RUN groupadd --gid $USER_GID bytes
-RUN adduser --disabled-password --gecos '' --uid $USER_UID --gid $USER_GID bytes
+RUN groupadd --gid "$USER_GID" bytes
+RUN adduser --disabled-password --gecos '' --uid "$USER_UID" --gid "$USER_GID" bytes
 
 WORKDIR /app/bytes
 ENV PATH=/home/bytes/.local/bin:${PATH}
diff --git a/keiko/Dockerfile b/keiko/Dockerfile
index 71ecbee6634..865cfcb3efe 100644
--- a/keiko/Dockerfile
+++ b/keiko/Dockerfile
@@ -6,8 +6,8 @@ EXPOSE 8000
 ARG USER_UID=1000
 ARG USER_GID=1000
 
-RUN groupadd --gid $USER_GID keiko
-RUN adduser --disabled-password --gecos '' --uid $USER_UID --gid $USER_GID keiko
+RUN groupadd --gid "$USER_GID" keiko
+RUN adduser --disabled-password --gecos '' --uid "$USER_UID" --gid "$USER_GID" keiko
 
 WORKDIR /app/keiko
 ENV PATH=/home/keiko/.local/bin:${PATH}
diff --git a/mula/Dockerfile b/mula/Dockerfile
index 19c314b8200..4ac6ed198ca 100644
--- a/mula/Dockerfile
+++ b/mula/Dockerfile
@@ -8,8 +8,8 @@ ARG USER_GID=1000
 
 ENTRYPOINT ["/app/scheduler/entrypoint.sh"]
 
-RUN groupadd --gid $USER_GID scheduler
-RUN adduser --disabled-password --gecos '' --uid $USER_UID --gid $USER_GID scheduler
+RUN groupadd --gid "$USER_GID" scheduler
+RUN adduser --disabled-password --gecos '' --uid "$USER_UID" --gid "$USER_GID" scheduler
 
 WORKDIR /app/scheduler
 ENV PATH=/home/scheduler/.local/bin:${PATH}
diff --git a/octopoes/Dockerfile b/octopoes/Dockerfile
index 4e3afc00791..0eee18583a9 100644
--- a/octopoes/Dockerfile
+++ b/octopoes/Dockerfile
@@ -10,8 +10,8 @@ WORKDIR /app/octopoes
 
 ENTRYPOINT ["/app/octopoes/entrypoint.sh"]
 
-RUN groupadd --gid $USER_GID octopoes
-RUN adduser --disabled-password --gecos '' --uid $USER_UID --gid $USER_GID octopoes
+RUN groupadd --gid "$USER_GID" octopoes
+RUN adduser --disabled-password --gecos '' --uid "$USER_UID" --gid "$USER_GID" octopoes
 
 ENV PATH=/home/octopoes/.local/bin:${PATH}
 
diff --git a/rocky/Dockerfile b/rocky/Dockerfile
index c16bf4593d7..093e020652e 100644
--- a/rocky/Dockerfile
+++ b/rocky/Dockerfile
@@ -19,8 +19,8 @@ ARG USER_GID=1000
 
 ENTRYPOINT ["/app/rocky/entrypoint.sh"]
 
-RUN groupadd --gid $USER_GID rocky
-RUN adduser --disabled-password --gecos '' --uid $USER_UID --gid $USER_GID rocky
+RUN groupadd --gid "$USER_GID" rocky
+RUN adduser --disabled-password --gecos '' --uid "$USER_UID" --gid "$USER_GID" rocky
 
 WORKDIR /app/rocky