diff --git a/build_library/build_image_util.sh b/build_library/build_image_util.sh
index 25a59225bc..13bbbfd09f 100755
--- a/build_library/build_image_util.sh
+++ b/build_library/build_image_util.sh
@@ -163,6 +163,24 @@ package_provided() {
     done
 }
 
+assert_image_size() {
+  local disk_img="$1"
+  local disk_type="$2"
+
+  local size
+  size=$(qemu-img info -f "${disk_type}" --output json "${disk_img}" | \
+      gawk 'match($0, /"virtual-size": ([0-9]+),/, val) {print val[1]}' ; \
+      exit ${PIPESTATUS[0]})
+  if [[ $? -ne 0 ]]; then
+    die_notrace "assert failed: could not read image size"
+  fi
+
+  MiB=$((1024*1024))
+  if [[ $(($size % $MiB)) -ne 0 ]]; then
+    die_notrace "assert failed: image must be a multiple of 1 MiB ($size B)"
+  fi
+}
+
 start_image() {
   local image_name="$1"
   local disk_layout="$2"
@@ -181,6 +199,8 @@ start_image() {
   "${BUILD_LIBRARY_DIR}/disk_util" --disk_layout="${disk_layout}" \
       format "${disk_img}"
 
+  assert_image_size "${disk_img}" raw
+
   "${BUILD_LIBRARY_DIR}/disk_util" --disk_layout="${disk_layout}" \
       mount "${disk_img}" "${root_fs_dir}"
   trap "cleanup_mounts '${root_fs_dir}' && delete_prompt" EXIT
diff --git a/build_library/disk_layout.json b/build_library/disk_layout.json
index 77c8048bf4..ec59424785 100644
--- a/build_library/disk_layout.json
+++ b/build_library/disk_layout.json
@@ -76,6 +76,12 @@
         "blocks":"12689408"
       }
     },
+    "azure":{
+      "9":{
+        "label":"ROOT",
+        "blocks":"58752990"
+      }
+    },
     "vagrant":{
       "9":{
         "label":"ROOT",
diff --git a/build_library/vm_image_util.sh b/build_library/vm_image_util.sh
index f52a28bd90..8d3c96d40a 100644
--- a/build_library/vm_image_util.sh
+++ b/build_library/vm_image_util.sh
@@ -211,6 +211,7 @@ IMG_exoscale_OEM_PACKAGE=oem-exoscale
 ## azure
 IMG_azure_BOOT_KERNEL=0
 IMG_azure_DISK_FORMAT=vhd
+IMG_azure_DISK_LAYOUT=azure
 IMG_azure_OEM_PACKAGE=oem-azure
 
 ## hyper-v
@@ -331,6 +332,8 @@ setup_disk_image() {
           update "${VM_TMP_IMG}"
     fi
 
+    assert_image_size "${VM_TMP_IMG}" raw
+
     info "Mounting image to $(relpath "${VM_TMP_ROOT}")"
     "${BUILD_LIBRARY_DIR}/disk_util" --disk_layout="${disk_layout}" \
         mount "${VM_TMP_IMG}" "${VM_TMP_ROOT}"
@@ -432,18 +435,22 @@ _write_raw_disk() {
 
 _write_qcow2_disk() {
     qemu-img convert -f raw "$1" -O qcow2 "$2"
+    assert_image_size "$2" qcow2
 }
 
 _write_vhd_disk() {
     qemu-img convert -f raw "$1" -O vpc "$2"
+    assert_image_size "$2" vpc
 }
 
 _write_vmdk_ide_disk() {
     qemu-img convert -f raw "$1" -O vmdk -o adapter_type=ide "$2"
+    assert_image_size "$2" vmdk
 }
 
 _write_vmdk_scsi_disk() {
     qemu-img convert -f raw "$1" -O vmdk -o adapter_type=lsilogic "$2"
+    assert_image_size "$2" vmdk
 }
 
 _write_cpio_common() {