diff --git a/13-to-14/Dockerfile b/13-to-14/Dockerfile
index 8e907ce..928f50e 100644
--- a/13-to-14/Dockerfile
+++ b/13-to-14/Dockerfile
@@ -15,11 +15,11 @@ RUN set -eux; \
 	; \
 	rm -rf /var/lib/apt/lists/*
 
-ENV PGBINOLD /usr/lib/postgresql/13/bin
-ENV PGBINNEW /usr/lib/postgresql/14/bin
+ENV PGBINOLD=/usr/lib/postgresql/13/bin
+ENV PGBINNEW=/usr/lib/postgresql/14/bin
 
-ENV PGDATAOLD /var/lib/postgresql/13/data
-ENV PGDATANEW /var/lib/postgresql/14/data
+ENV PGDATAOLD=/var/lib/postgresql/13/data
+ENV PGDATANEW=/var/lib/postgresql/14/data
 
 RUN set -eux; \
 	mkdir -p "$PGDATAOLD" "$PGDATANEW"; \
diff --git a/13-to-14/docker-upgrade b/13-to-14/docker-upgrade
index c8c0699..509f4c7 100755
--- a/13-to-14/docker-upgrade
+++ b/13-to-14/docker-upgrade
@@ -13,6 +13,10 @@ if [ "$1" = 'pg_upgrade' -a "$(id -u)" = '0' ]; then
 	exec gosu postgres "$BASH_SOURCE" "$@"
 fi
 
+if [[ -n "$PGUSER" && ! "$POSTGRES_INITDB_ARGS" =~ ((--username=|-U[[:space:]])) ]]; then
+    POSTGRES_INITDB_ARGS+=" --username=$PGUSER"
+fi
+
 if [ "$1" = 'pg_upgrade' ]; then
 	if [ ! -s "$PGDATANEW/PG_VERSION" ]; then
 		PGDATA="$PGDATANEW" eval "initdb $POSTGRES_INITDB_ARGS"
diff --git a/13-to-15/Dockerfile b/13-to-15/Dockerfile
index c0da60e..369ee7f 100644
--- a/13-to-15/Dockerfile
+++ b/13-to-15/Dockerfile
@@ -15,11 +15,11 @@ RUN set -eux; \
 	; \
 	rm -rf /var/lib/apt/lists/*
 
-ENV PGBINOLD /usr/lib/postgresql/13/bin
-ENV PGBINNEW /usr/lib/postgresql/15/bin
+ENV PGBINOLD=/usr/lib/postgresql/13/bin
+ENV PGBINNEW=/usr/lib/postgresql/15/bin
 
-ENV PGDATAOLD /var/lib/postgresql/13/data
-ENV PGDATANEW /var/lib/postgresql/15/data
+ENV PGDATAOLD=/var/lib/postgresql/13/data
+ENV PGDATANEW=/var/lib/postgresql/15/data
 
 RUN set -eux; \
 	mkdir -p "$PGDATAOLD" "$PGDATANEW"; \
diff --git a/13-to-15/docker-upgrade b/13-to-15/docker-upgrade
index c8c0699..509f4c7 100755
--- a/13-to-15/docker-upgrade
+++ b/13-to-15/docker-upgrade
@@ -13,6 +13,10 @@ if [ "$1" = 'pg_upgrade' -a "$(id -u)" = '0' ]; then
 	exec gosu postgres "$BASH_SOURCE" "$@"
 fi
 
+if [[ -n "$PGUSER" && ! "$POSTGRES_INITDB_ARGS" =~ ((--username=|-U[[:space:]])) ]]; then
+    POSTGRES_INITDB_ARGS+=" --username=$PGUSER"
+fi
+
 if [ "$1" = 'pg_upgrade' ]; then
 	if [ ! -s "$PGDATANEW/PG_VERSION" ]; then
 		PGDATA="$PGDATANEW" eval "initdb $POSTGRES_INITDB_ARGS"
diff --git a/13-to-16/Dockerfile b/13-to-16/Dockerfile
index 444b8e3..3d65e02 100644
--- a/13-to-16/Dockerfile
+++ b/13-to-16/Dockerfile
@@ -15,11 +15,11 @@ RUN set -eux; \
 	; \
 	rm -rf /var/lib/apt/lists/*
 
-ENV PGBINOLD /usr/lib/postgresql/13/bin
-ENV PGBINNEW /usr/lib/postgresql/16/bin
+ENV PGBINOLD=/usr/lib/postgresql/13/bin
+ENV PGBINNEW=/usr/lib/postgresql/16/bin
 
-ENV PGDATAOLD /var/lib/postgresql/13/data
-ENV PGDATANEW /var/lib/postgresql/16/data
+ENV PGDATAOLD=/var/lib/postgresql/13/data
+ENV PGDATANEW=/var/lib/postgresql/16/data
 
 RUN set -eux; \
 	mkdir -p "$PGDATAOLD" "$PGDATANEW"; \
diff --git a/13-to-16/docker-upgrade b/13-to-16/docker-upgrade
index c8c0699..509f4c7 100755
--- a/13-to-16/docker-upgrade
+++ b/13-to-16/docker-upgrade
@@ -13,6 +13,10 @@ if [ "$1" = 'pg_upgrade' -a "$(id -u)" = '0' ]; then
 	exec gosu postgres "$BASH_SOURCE" "$@"
 fi
 
+if [[ -n "$PGUSER" && ! "$POSTGRES_INITDB_ARGS" =~ ((--username=|-U[[:space:]])) ]]; then
+    POSTGRES_INITDB_ARGS+=" --username=$PGUSER"
+fi
+
 if [ "$1" = 'pg_upgrade' ]; then
 	if [ ! -s "$PGDATANEW/PG_VERSION" ]; then
 		PGDATA="$PGDATANEW" eval "initdb $POSTGRES_INITDB_ARGS"
diff --git a/13-to-17/Dockerfile b/13-to-17/Dockerfile
index 145d1da..52774ff 100644
--- a/13-to-17/Dockerfile
+++ b/13-to-17/Dockerfile
@@ -15,11 +15,11 @@ RUN set -eux; \
 	; \
 	rm -rf /var/lib/apt/lists/*
 
-ENV PGBINOLD /usr/lib/postgresql/13/bin
-ENV PGBINNEW /usr/lib/postgresql/17/bin
+ENV PGBINOLD=/usr/lib/postgresql/13/bin
+ENV PGBINNEW=/usr/lib/postgresql/17/bin
 
-ENV PGDATAOLD /var/lib/postgresql/13/data
-ENV PGDATANEW /var/lib/postgresql/17/data
+ENV PGDATAOLD=/var/lib/postgresql/13/data
+ENV PGDATANEW=/var/lib/postgresql/17/data
 
 RUN set -eux; \
 	mkdir -p "$PGDATAOLD" "$PGDATANEW"; \
diff --git a/13-to-17/docker-upgrade b/13-to-17/docker-upgrade
index c8c0699..509f4c7 100755
--- a/13-to-17/docker-upgrade
+++ b/13-to-17/docker-upgrade
@@ -13,6 +13,10 @@ if [ "$1" = 'pg_upgrade' -a "$(id -u)" = '0' ]; then
 	exec gosu postgres "$BASH_SOURCE" "$@"
 fi
 
+if [[ -n "$PGUSER" && ! "$POSTGRES_INITDB_ARGS" =~ ((--username=|-U[[:space:]])) ]]; then
+    POSTGRES_INITDB_ARGS+=" --username=$PGUSER"
+fi
+
 if [ "$1" = 'pg_upgrade' ]; then
 	if [ ! -s "$PGDATANEW/PG_VERSION" ]; then
 		PGDATA="$PGDATANEW" eval "initdb $POSTGRES_INITDB_ARGS"
diff --git a/14-to-15/Dockerfile b/14-to-15/Dockerfile
index cf370ee..4b323b2 100644
--- a/14-to-15/Dockerfile
+++ b/14-to-15/Dockerfile
@@ -15,11 +15,11 @@ RUN set -eux; \
 	; \
 	rm -rf /var/lib/apt/lists/*
 
-ENV PGBINOLD /usr/lib/postgresql/14/bin
-ENV PGBINNEW /usr/lib/postgresql/15/bin
+ENV PGBINOLD=/usr/lib/postgresql/14/bin
+ENV PGBINNEW=/usr/lib/postgresql/15/bin
 
-ENV PGDATAOLD /var/lib/postgresql/14/data
-ENV PGDATANEW /var/lib/postgresql/15/data
+ENV PGDATAOLD=/var/lib/postgresql/14/data
+ENV PGDATANEW=/var/lib/postgresql/15/data
 
 RUN set -eux; \
 	mkdir -p "$PGDATAOLD" "$PGDATANEW"; \
diff --git a/14-to-15/docker-upgrade b/14-to-15/docker-upgrade
index c8c0699..509f4c7 100755
--- a/14-to-15/docker-upgrade
+++ b/14-to-15/docker-upgrade
@@ -13,6 +13,10 @@ if [ "$1" = 'pg_upgrade' -a "$(id -u)" = '0' ]; then
 	exec gosu postgres "$BASH_SOURCE" "$@"
 fi
 
+if [[ -n "$PGUSER" && ! "$POSTGRES_INITDB_ARGS" =~ ((--username=|-U[[:space:]])) ]]; then
+    POSTGRES_INITDB_ARGS+=" --username=$PGUSER"
+fi
+
 if [ "$1" = 'pg_upgrade' ]; then
 	if [ ! -s "$PGDATANEW/PG_VERSION" ]; then
 		PGDATA="$PGDATANEW" eval "initdb $POSTGRES_INITDB_ARGS"
diff --git a/14-to-16/Dockerfile b/14-to-16/Dockerfile
index 72ce29d..5bd0f89 100644
--- a/14-to-16/Dockerfile
+++ b/14-to-16/Dockerfile
@@ -15,11 +15,11 @@ RUN set -eux; \
 	; \
 	rm -rf /var/lib/apt/lists/*
 
-ENV PGBINOLD /usr/lib/postgresql/14/bin
-ENV PGBINNEW /usr/lib/postgresql/16/bin
+ENV PGBINOLD=/usr/lib/postgresql/14/bin
+ENV PGBINNEW=/usr/lib/postgresql/16/bin
 
-ENV PGDATAOLD /var/lib/postgresql/14/data
-ENV PGDATANEW /var/lib/postgresql/16/data
+ENV PGDATAOLD=/var/lib/postgresql/14/data
+ENV PGDATANEW=/var/lib/postgresql/16/data
 
 RUN set -eux; \
 	mkdir -p "$PGDATAOLD" "$PGDATANEW"; \
diff --git a/14-to-16/docker-upgrade b/14-to-16/docker-upgrade
index c8c0699..509f4c7 100755
--- a/14-to-16/docker-upgrade
+++ b/14-to-16/docker-upgrade
@@ -13,6 +13,10 @@ if [ "$1" = 'pg_upgrade' -a "$(id -u)" = '0' ]; then
 	exec gosu postgres "$BASH_SOURCE" "$@"
 fi
 
+if [[ -n "$PGUSER" && ! "$POSTGRES_INITDB_ARGS" =~ ((--username=|-U[[:space:]])) ]]; then
+    POSTGRES_INITDB_ARGS+=" --username=$PGUSER"
+fi
+
 if [ "$1" = 'pg_upgrade' ]; then
 	if [ ! -s "$PGDATANEW/PG_VERSION" ]; then
 		PGDATA="$PGDATANEW" eval "initdb $POSTGRES_INITDB_ARGS"
diff --git a/14-to-17/Dockerfile b/14-to-17/Dockerfile
index 2cec8e9..1e8d53d 100644
--- a/14-to-17/Dockerfile
+++ b/14-to-17/Dockerfile
@@ -15,11 +15,11 @@ RUN set -eux; \
 	; \
 	rm -rf /var/lib/apt/lists/*
 
-ENV PGBINOLD /usr/lib/postgresql/14/bin
-ENV PGBINNEW /usr/lib/postgresql/17/bin
+ENV PGBINOLD=/usr/lib/postgresql/14/bin
+ENV PGBINNEW=/usr/lib/postgresql/17/bin
 
-ENV PGDATAOLD /var/lib/postgresql/14/data
-ENV PGDATANEW /var/lib/postgresql/17/data
+ENV PGDATAOLD=/var/lib/postgresql/14/data
+ENV PGDATANEW=/var/lib/postgresql/17/data
 
 RUN set -eux; \
 	mkdir -p "$PGDATAOLD" "$PGDATANEW"; \
diff --git a/14-to-17/docker-upgrade b/14-to-17/docker-upgrade
index c8c0699..509f4c7 100755
--- a/14-to-17/docker-upgrade
+++ b/14-to-17/docker-upgrade
@@ -13,6 +13,10 @@ if [ "$1" = 'pg_upgrade' -a "$(id -u)" = '0' ]; then
 	exec gosu postgres "$BASH_SOURCE" "$@"
 fi
 
+if [[ -n "$PGUSER" && ! "$POSTGRES_INITDB_ARGS" =~ ((--username=|-U[[:space:]])) ]]; then
+    POSTGRES_INITDB_ARGS+=" --username=$PGUSER"
+fi
+
 if [ "$1" = 'pg_upgrade' ]; then
 	if [ ! -s "$PGDATANEW/PG_VERSION" ]; then
 		PGDATA="$PGDATANEW" eval "initdb $POSTGRES_INITDB_ARGS"
diff --git a/15-to-16/Dockerfile b/15-to-16/Dockerfile
index 22b5a39..22fc47d 100644
--- a/15-to-16/Dockerfile
+++ b/15-to-16/Dockerfile
@@ -15,11 +15,11 @@ RUN set -eux; \
 	; \
 	rm -rf /var/lib/apt/lists/*
 
-ENV PGBINOLD /usr/lib/postgresql/15/bin
-ENV PGBINNEW /usr/lib/postgresql/16/bin
+ENV PGBINOLD=/usr/lib/postgresql/15/bin
+ENV PGBINNEW=/usr/lib/postgresql/16/bin
 
-ENV PGDATAOLD /var/lib/postgresql/15/data
-ENV PGDATANEW /var/lib/postgresql/16/data
+ENV PGDATAOLD=/var/lib/postgresql/15/data
+ENV PGDATANEW=/var/lib/postgresql/16/data
 
 RUN set -eux; \
 	mkdir -p "$PGDATAOLD" "$PGDATANEW"; \
diff --git a/15-to-16/docker-upgrade b/15-to-16/docker-upgrade
index c8c0699..509f4c7 100755
--- a/15-to-16/docker-upgrade
+++ b/15-to-16/docker-upgrade
@@ -13,6 +13,10 @@ if [ "$1" = 'pg_upgrade' -a "$(id -u)" = '0' ]; then
 	exec gosu postgres "$BASH_SOURCE" "$@"
 fi
 
+if [[ -n "$PGUSER" && ! "$POSTGRES_INITDB_ARGS" =~ ((--username=|-U[[:space:]])) ]]; then
+    POSTGRES_INITDB_ARGS+=" --username=$PGUSER"
+fi
+
 if [ "$1" = 'pg_upgrade' ]; then
 	if [ ! -s "$PGDATANEW/PG_VERSION" ]; then
 		PGDATA="$PGDATANEW" eval "initdb $POSTGRES_INITDB_ARGS"
diff --git a/15-to-17/Dockerfile b/15-to-17/Dockerfile
index 10ef8ff..1cf4e1f 100644
--- a/15-to-17/Dockerfile
+++ b/15-to-17/Dockerfile
@@ -15,11 +15,11 @@ RUN set -eux; \
 	; \
 	rm -rf /var/lib/apt/lists/*
 
-ENV PGBINOLD /usr/lib/postgresql/15/bin
-ENV PGBINNEW /usr/lib/postgresql/17/bin
+ENV PGBINOLD=/usr/lib/postgresql/15/bin
+ENV PGBINNEW=/usr/lib/postgresql/17/bin
 
-ENV PGDATAOLD /var/lib/postgresql/15/data
-ENV PGDATANEW /var/lib/postgresql/17/data
+ENV PGDATAOLD=/var/lib/postgresql/15/data
+ENV PGDATANEW=/var/lib/postgresql/17/data
 
 RUN set -eux; \
 	mkdir -p "$PGDATAOLD" "$PGDATANEW"; \
diff --git a/15-to-17/docker-upgrade b/15-to-17/docker-upgrade
index c8c0699..509f4c7 100755
--- a/15-to-17/docker-upgrade
+++ b/15-to-17/docker-upgrade
@@ -13,6 +13,10 @@ if [ "$1" = 'pg_upgrade' -a "$(id -u)" = '0' ]; then
 	exec gosu postgres "$BASH_SOURCE" "$@"
 fi
 
+if [[ -n "$PGUSER" && ! "$POSTGRES_INITDB_ARGS" =~ ((--username=|-U[[:space:]])) ]]; then
+    POSTGRES_INITDB_ARGS+=" --username=$PGUSER"
+fi
+
 if [ "$1" = 'pg_upgrade' ]; then
 	if [ ! -s "$PGDATANEW/PG_VERSION" ]; then
 		PGDATA="$PGDATANEW" eval "initdb $POSTGRES_INITDB_ARGS"
diff --git a/16-to-17/Dockerfile b/16-to-17/Dockerfile
index fcf5c9b..07a965b 100644
--- a/16-to-17/Dockerfile
+++ b/16-to-17/Dockerfile
@@ -15,11 +15,11 @@ RUN set -eux; \
 	; \
 	rm -rf /var/lib/apt/lists/*
 
-ENV PGBINOLD /usr/lib/postgresql/16/bin
-ENV PGBINNEW /usr/lib/postgresql/17/bin
+ENV PGBINOLD=/usr/lib/postgresql/16/bin
+ENV PGBINNEW=/usr/lib/postgresql/17/bin
 
-ENV PGDATAOLD /var/lib/postgresql/16/data
-ENV PGDATANEW /var/lib/postgresql/17/data
+ENV PGDATAOLD=/var/lib/postgresql/16/data
+ENV PGDATANEW=/var/lib/postgresql/17/data
 
 RUN set -eux; \
 	mkdir -p "$PGDATAOLD" "$PGDATANEW"; \
diff --git a/16-to-17/docker-upgrade b/16-to-17/docker-upgrade
index c8c0699..509f4c7 100755
--- a/16-to-17/docker-upgrade
+++ b/16-to-17/docker-upgrade
@@ -13,6 +13,10 @@ if [ "$1" = 'pg_upgrade' -a "$(id -u)" = '0' ]; then
 	exec gosu postgres "$BASH_SOURCE" "$@"
 fi
 
+if [[ -n "$PGUSER" && ! "$POSTGRES_INITDB_ARGS" =~ ((--username=|-U[[:space:]])) ]]; then
+    POSTGRES_INITDB_ARGS+=" --username=$PGUSER"
+fi
+
 if [ "$1" = 'pg_upgrade' ]; then
 	if [ ! -s "$PGDATANEW/PG_VERSION" ]; then
 		PGDATA="$PGDATANEW" eval "initdb $POSTGRES_INITDB_ARGS"
diff --git a/Dockerfile.template b/Dockerfile.template
index 287e789..09b1fa6 100644
--- a/Dockerfile.template
+++ b/Dockerfile.template
@@ -9,11 +9,11 @@ RUN set -eux; \
 	; \
 	rm -rf /var/lib/apt/lists/*
 
-ENV PGBINOLD /usr/lib/postgresql/{{ .old }}/bin
-ENV PGBINNEW /usr/lib/postgresql/{{ .new }}/bin
+ENV PGBINOLD=/usr/lib/postgresql/{{ .old }}/bin
+ENV PGBINNEW=/usr/lib/postgresql/{{ .new }}/bin
 
-ENV PGDATAOLD /var/lib/postgresql/{{ .old }}/data
-ENV PGDATANEW /var/lib/postgresql/{{ .new }}/data
+ENV PGDATAOLD=/var/lib/postgresql/{{ .old }}/data
+ENV PGDATANEW=/var/lib/postgresql/{{ .new }}/data
 
 RUN set -eux; \
 	mkdir -p "$PGDATAOLD" "$PGDATANEW"; \
diff --git a/docker-upgrade b/docker-upgrade
index c8c0699..509f4c7 100755
--- a/docker-upgrade
+++ b/docker-upgrade
@@ -13,6 +13,10 @@ if [ "$1" = 'pg_upgrade' -a "$(id -u)" = '0' ]; then
 	exec gosu postgres "$BASH_SOURCE" "$@"
 fi
 
+if [[ -n "$PGUSER" && ! "$POSTGRES_INITDB_ARGS" =~ ((--username=|-U[[:space:]])) ]]; then
+    POSTGRES_INITDB_ARGS+=" --username=$PGUSER"
+fi
+
 if [ "$1" = 'pg_upgrade' ]; then
 	if [ ! -s "$PGDATANEW/PG_VERSION" ]; then
 		PGDATA="$PGDATANEW" eval "initdb $POSTGRES_INITDB_ARGS"