diff --git a/primary.tf b/primary.tf
index 78571120..664ab632 100644
--- a/primary.tf
+++ b/primary.tf
@@ -1,5 +1,8 @@
 resource "aws_instance" "primary" {
-  count         = "${var.primary_count}"
+  /* The number of primaries must be hard coded to 3 when Internal Production Mode
+  is selected. Currently, that mode does not support scaling. In other modes, the 
+  cluster can be scaled according the primary_count variable. */
+  count         = "${var.install_type == "ipm" ? 3 : var.primary_count}"
   ami           = "${var.ami != "" ? var.ami : local.distro_ami}"
   instance_type = "${var.primary_instance_type}"
 
diff --git a/variables.tf b/variables.tf
index e96dfa7d..f212be23 100644
--- a/variables.tf
+++ b/variables.tf
@@ -110,7 +110,7 @@ variable "installer_url" {
 
 variable "primary_count" {
   type        = "string"
-  description = "The number of additional cluster master nodes to run"
+  description = "The number of primary cluster master nodes to run, should be 3 or 5."
   default     = 3
 }