diff --git a/lib/image-stream/handlers.js b/lib/image-stream/handlers.js
index 04f1c527..6c32d50a 100644
--- a/lib/image-stream/handlers.js
+++ b/lib/image-stream/handlers.js
@@ -33,6 +33,13 @@ const fileExtensions = require('../shared/file-extensions')
 const path = require('path')
 const errors = require('../shared/errors')
 
+/**
+ * @summary Default image extension to be assumed
+ * @type {String}
+ * @constant
+ */
+const DEFAULT_EXT = 'img'
+
 /**
  * @summary Image handlers
  * @namespace handlers
@@ -57,7 +64,7 @@ module.exports = {
     return {
       path: imagePath,
       archiveExtension: fileExtensions.getLastFileExtension(imagePath),
-      extension: fileExtensions.getPenultimateFileExtension(imagePath),
+      extension: fileExtensions.getPenultimateFileExtension(imagePath) || DEFAULT_EXT,
       stream: fs.createReadStream(imagePath),
       size: {
         original: options.size,
@@ -97,7 +104,7 @@ module.exports = {
       return {
         path: imagePath,
         archiveExtension: fileExtensions.getLastFileExtension(imagePath),
-        extension: fileExtensions.getPenultimateFileExtension(imagePath),
+        extension: fileExtensions.getPenultimateFileExtension(imagePath) || DEFAULT_EXT,
         stream: fs.createReadStream(imagePath),
         size: {
           original: options.size,
@@ -138,7 +145,7 @@ module.exports = {
       return {
         path: imagePath,
         archiveExtension: fileExtensions.getLastFileExtension(imagePath),
-        extension: fileExtensions.getPenultimateFileExtension(imagePath),
+        extension: fileExtensions.getPenultimateFileExtension(imagePath) || DEFAULT_EXT,
         stream: fs.createReadStream(imagePath),
         size: {
           original: options.size,
diff --git a/lib/shared/file-extensions.js b/lib/shared/file-extensions.js
index dd5a4eb6..05c27b92 100644
--- a/lib/shared/file-extensions.js
+++ b/lib/shared/file-extensions.js
@@ -16,6 +16,7 @@
 
 'use strict'
 
+const mime = require('mime-types')
 const _ = require('lodash')
 
 /**
@@ -45,15 +46,15 @@ exports.getFileExtensions = _.memoize((filePath) => {
  * @public
  *
  * @param {String} filePath - file path
- * @returns {(String|Undefined)} last extension
+ * @returns {(String|Null)} last extension
  *
  * @example
  * const extension = fileExtensions.getLastFileExtension('path/to/foo.img.gz');
  * console.log(extension);
- * > [ 'gz' ]
+ * > 'gz'
  */
 exports.getLastFileExtension = (filePath) => {
-  return _.last(exports.getFileExtensions(filePath))
+  return _.last(exports.getFileExtensions(filePath)) || null
 }
 
 /**
@@ -62,13 +63,14 @@ exports.getLastFileExtension = (filePath) => {
  * @public
  *
  * @param {String} filePath - file path
- * @returns {(String|Undefined)} penultimate extension
+ * @returns {(String|Null)} penultimate extension
  *
  * @example
  * const extension = fileExtensions.getPenultimateFileExtension('path/to/foo.img.gz');
  * console.log(extension);
- * > [ 'img' ]
+ * > 'img'
  */
 exports.getPenultimateFileExtension = (filePath) => {
-  return _.last(_.initial(exports.getFileExtensions(filePath)))
+  const ext = _.last(_.initial(exports.getFileExtensions(filePath)))
+  return !_.isNil(ext) && mime.lookup(ext) ? ext : null
 }
diff --git a/lib/shared/store.js b/lib/shared/store.js
index 5421b843..6141ea0c 100644
--- a/lib/shared/store.js
+++ b/lib/shared/store.js
@@ -311,6 +311,10 @@ const storeReducer = (state = DEFAULT_STATE, action) => {
       return state.setIn([ 'selection', 'drive' ], Immutable.fromJS(action.data))
     }
 
+    // TODO(jhermsmeier): Consolidate these assertions
+    // with image-stream / supported-formats, and have *one*
+    // place where all the image extension / format handling
+    // takes place, to avoid having to check 2+ locations with different logic
     case ACTIONS.SELECT_IMAGE: {
       if (!action.data.path) {
         throw errors.createError({
diff --git a/lib/shared/supported-formats.js b/lib/shared/supported-formats.js
index 86bad68c..8897df57 100644
--- a/lib/shared/supported-formats.js
+++ b/lib/shared/supported-formats.js
@@ -122,10 +122,15 @@ exports.isSupportedImage = (imagePath) => {
     return true
   }
 
-  return _.every([
+  if (_.every([
     _.includes(exports.getCompressedExtensions(), lastExtension),
     _.includes(exports.getNonCompressedExtensions(), penultimateExtension)
-  ])
+  ])) {
+    return true
+  }
+
+  return _.isNil(penultimateExtension) &&
+    _.includes(exports.getCompressedExtensions(), lastExtension)
 }
 
 /**
diff --git a/tests/shared/file-extensions.spec.js b/tests/shared/file-extensions.spec.js
index 8f023d17..7acc037f 100644
--- a/tests/shared/file-extensions.spec.js
+++ b/tests/shared/file-extensions.spec.js
@@ -101,7 +101,7 @@ describe('Shared: fileExtensions', function () {
 
   describe('.getLastFileExtension()', function () {
     it('should return undefined if the file path has no extension', function () {
-      m.chai.expect(fileExtensions.getLastFileExtension('foo')).to.be.undefined
+      m.chai.expect(fileExtensions.getLastFileExtension('foo')).to.equal(null)
     })
 
     it('should return the extension if there is only one extension', function () {
@@ -119,11 +119,11 @@ describe('Shared: fileExtensions', function () {
 
   describe('.getPenultimateFileExtension()', function () {
     it('should return undefined in the file path has no extension', function () {
-      m.chai.expect(fileExtensions.getPenultimateFileExtension('foo')).to.be.undefined
+      m.chai.expect(fileExtensions.getPenultimateFileExtension('foo')).to.equal(null)
     })
 
     it('should return undefined if there is only one extension', function () {
-      m.chai.expect(fileExtensions.getPenultimateFileExtension('foo.img')).to.be.undefined
+      m.chai.expect(fileExtensions.getPenultimateFileExtension('foo.img')).to.equal(null)
     })
 
     it('should return the penultimate extension if there are two extensions', function () {
diff --git a/tests/shared/models/selection-state.spec.js b/tests/shared/models/selection-state.spec.js
index 13c94065..cc71c249 100644
--- a/tests/shared/models/selection-state.spec.js
+++ b/tests/shared/models/selection-state.spec.js
@@ -370,6 +370,42 @@ describe('Model: selectionState', function () {
         m.chai.expect(imagePath).to.equal('foo.zip')
       })
 
+      it('should infer a compressed raw image if the penultimate extension is missing', function () {
+        selectionState.setImage({
+          path: 'foo.xz',
+          extension: 'img',
+          archiveExtension: 'xz',
+          size: {
+            original: 999999999,
+            final: {
+              estimation: false,
+              value: 999999999
+            }
+          }
+        })
+
+        const imagePath = selectionState.getImagePath()
+        m.chai.expect(imagePath).to.equal('foo.xz')
+      })
+
+      it('should infer a compressed raw image if the penultimate extension is not a file extension', function () {
+        selectionState.setImage({
+          path: 'something.linux-x86-64.gz',
+          extension: 'img',
+          archiveExtension: 'gz',
+          size: {
+            original: 999999999,
+            final: {
+              estimation: false,
+              value: 999999999
+            }
+          }
+        })
+
+        const imagePath = selectionState.getImagePath()
+        m.chai.expect(imagePath).to.equal('something.linux-x86-64.gz')
+      })
+
       it('should throw if no path', function () {
         m.chai.expect(function () {
           selectionState.setImage({