diff --git a/minecraft/Dockerfile b/minecraft/Dockerfile
index 11809d8..693b2d9 100644
--- a/minecraft/Dockerfile
+++ b/minecraft/Dockerfile
@@ -14,9 +14,9 @@ ENV FABRIC_VERSION=""
 ENV FABRIC_INSTALLER_VERSION=""
 
 # RCON settings.
-ENV ENABLE_RCON=
-ENV RCON_PORT=
-ENV RCON_PASSWORD=
+ENV ENABLE_RCON=""
+ENV RCON_PORT=""
+ENV RCON_PASSWORD=""
 
 # Java settings.
 ENV JAVA_VERSION=""
diff --git a/testing/Dockerfile b/testing/Dockerfile
index 4ca9eac..7385291 100644
--- a/testing/Dockerfile
+++ b/testing/Dockerfile
@@ -14,9 +14,9 @@ ENV FABRIC_VERSION=""
 ENV FABRIC_INSTALLER_VERSION=""
 
 # RCON settings.
-ENV ENABLE_RCON=
-ENV RCON_PORT=
-ENV RCON_PASSWORD=
+ENV ENABLE_RCON=""
+ENV RCON_PORT=""
+ENV RCON_PASSWORD=""
 
 # Java settings.
 ENV JAVA_VERSION=""