diff --git a/Debian/Dockerfile.template b/Debian/Dockerfile.template
index 91304355..76ed00ca 100644
--- a/Debian/Dockerfile.template
+++ b/Debian/Dockerfile.template
@@ -31,9 +31,9 @@ COPY requirements.txt /
 # Install additional extensions
 RUN set -xe; \
 	apt-get update; \
-	if apt list --upgradable 2>/dev/null | grep -q '^postgres'; then \
+	if apt-get -s upgrade | grep "^Inst postgres"; then \
 		echo "ERROR: Upgradable postgres packages found!"; \
-		apt list --upgradable 2>/dev/null | grep '^postgres'; \
+		apt-get -s upgrade | grep "^Inst postgres"; \
 		exit 1; \
 	fi; \
 	apt-get install -y --no-install-recommends \