diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index fe03f716f3..53c62fb77c 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -180,6 +180,17 @@ static void s390_memory_init(MemoryRegion *ram)
 {
     MemoryRegion *sysmem = get_system_memory();
 
+    if (!QEMU_IS_ALIGNED(memory_region_size(ram), 1 * MiB)) {
+        /*
+         * SCLP cannot possibly expose smaller granularity right now and KVM
+         * cannot handle smaller granularity. As we don't support NUMA, the
+         * region size directly corresponds to machine->ram_size, and the region
+         * is a single RAM memory region.
+         */
+        error_report("ram size must be multiples of 1 MiB");
+        exit(EXIT_FAILURE);
+    }
+
     /* allocate RAM for core */
     memory_region_add_subregion(sysmem, 0, ram);