diff --git a/src/__tests__/fixtures/invalid-version-file/lib/test-gem/version.rb b/src/__tests__/fixtures/invalid-version-file/lib/test-gem/version.rb
new file mode 100644
index 0000000..a17bd89
--- /dev/null
+++ b/src/__tests__/fixtures/invalid-version-file/lib/test-gem/version.rb
@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+module TestGem
+  SOME_CONST = '1.1.2'
+end
diff --git a/src/__tests__/fixtures/invalid-version-file/test-gem.gemspec b/src/__tests__/fixtures/invalid-version-file/test-gem.gemspec
new file mode 100644
index 0000000..fe80e19
--- /dev/null
+++ b/src/__tests__/fixtures/invalid-version-file/test-gem.gemspec
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+lib = File.expand_path('lib', __dir__)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+
+require 'test-gem/version'
+
+Gem::Specification.new do |spec|
+  spec.name          = 'a-test-gem'
+  spec.version       = TestGem::SOME_CONST
+  spec.authors       = ['Rylan Collins']
+  spec.summary       = 'A gem for testing'
+end
diff --git a/src/__tests__/fixtures/prerelease/lib/test-gem/version.rb b/src/__tests__/fixtures/prerelease/lib/test-gem/version.rb
new file mode 100644
index 0000000..09bdedd
--- /dev/null
+++ b/src/__tests__/fixtures/prerelease/lib/test-gem/version.rb
@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+module TestGem
+  VERSION = '0.1.0.alpha.1'
+end
diff --git a/src/__tests__/fixtures/prerelease/test-gem.gemspec b/src/__tests__/fixtures/prerelease/test-gem.gemspec
new file mode 100644
index 0000000..e7e46ab
--- /dev/null
+++ b/src/__tests__/fixtures/prerelease/test-gem.gemspec
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+lib = File.expand_path('lib', __dir__)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+
+require 'test-gem/version'
+
+Gem::Specification.new do |spec|
+  spec.name          = 'a-test-gem'
+  spec.version       = TestGem::VERSION
+  spec.authors       = ['Rylan Collins']
+  spec.summary       = 'A gem for testing'
+end
diff --git a/src/__tests__/prepare.test.js b/src/__tests__/prepare.test.js
index 2b7c71f..6cc55aa 100644
--- a/src/__tests__/prepare.test.js
+++ b/src/__tests__/prepare.test.js
@@ -44,6 +44,23 @@ end
 `);
 });
 
+describe('when the version.rb contains a prerelease version', () => {
+  it('writes the new version to the version.rb file', async () => {
+    await prepare(
+      {},
+      { ...context, nextRelease: { version: '1.0.0-alpha.1' } },
+      { versionFile, gemspec, gemName },
+    );
+    const versionContents = await readFile(path.resolve(cwd, versionFile), 'utf8');
+    expect(versionContents).toEqual(`# frozen_string_literal: true
+
+module TestGem
+  VERSION = '1.0.0-alpha.1'
+end
+`);
+  });
+});
+
 describe('when updateGemfileLock is set to `true`', () => {
   it('runs `bundle install`', async () => {
     await writeFile(path.resolve(cwd, 'Gemfile'), "source 'https://rubygems.org'\ngemspec", 'utf8');
diff --git a/src/__tests__/verifyConditions.test.js b/src/__tests__/verifyConditions.test.js
index 5774c8e..83b07af 100644
--- a/src/__tests__/verifyConditions.test.js
+++ b/src/__tests__/verifyConditions.test.js
@@ -66,6 +66,17 @@ describe('when there is no version file', () => {
   });
 });
 
+describe('when no version can be found in the version file', () => {
+  it('throws an error', async () => {
+    const cwd = path.resolve(__dirname, './fixtures/invalid-version-file');
+    await expect(
+      verifyConditions({}, { cwd, env: defaultEnv }, { credentialsFile }),
+    ).rejects.toThrow(
+      /^Couldn't find a valid version constant defined in `lib\/test-gem\/version.rb`.$/,
+    );
+  });
+});
+
 it('creates the credentials file', async () => {
   await verifyConditions({}, { cwd: validCwd, env: defaultEnv }, { credentialsFile });
   const credentialsContents = await readFile(credentialsFile, 'utf8');
diff --git a/src/common.js b/src/common.js
new file mode 100644
index 0000000..8b3219b
--- /dev/null
+++ b/src/common.js
@@ -0,0 +1,2 @@
+// taken from https://github.com/svenfuchs/gem-release/blob/0f5f2382ef960d40169400a8aa25085cd37d26b0/lib/gem/release/files/version.rb#L7
+module.exports.VERSION_REGEX = /(VERSION\s*=\s*['"])(?:(?!"|').)*(['"])/;
diff --git a/src/prepare.js b/src/prepare.js
index d13ba08..b6500c2 100644
--- a/src/prepare.js
+++ b/src/prepare.js
@@ -1,16 +1,13 @@
 const { readFile, writeFile } = require('fs').promises;
 const path = require('path');
 const execa = require('execa');
+const { VERSION_REGEX } = require('./common');
 
 const writeVersion = async ({ versionFile, nextVersion, logger, cwd }) => {
   const fullVersionPath = path.resolve(cwd, versionFile);
   const versionContents = await readFile(fullVersionPath, 'utf8');
-  const newContents = versionContents.replace(
-    /(VERSION = ['"])[0-9.]*(['"])/,
-    `$1${nextVersion}$2`,
-  );
+  const newContents = versionContents.replace(VERSION_REGEX, `$1${nextVersion}$2`);
   logger.log('Writing version %s to `%s`', nextVersion, versionFile);
-  // TODO: Check to insure the contents changed. Or, maybe verify the format of the version in verify?
   await writeFile(fullVersionPath, newContents, 'utf8');
 };
 
diff --git a/src/verifyConditions.js b/src/verifyConditions.js
index 3b6117a..d001e01 100644
--- a/src/verifyConditions.js
+++ b/src/verifyConditions.js
@@ -1,10 +1,11 @@
 // const verifyConditions = require('./src/verify');
 const util = require('util');
 const execa = require('execa');
-const { writeFile } = require('fs').promises;
+const path = require('path');
+const { writeFile, readFile } = require('fs').promises;
 const SemanticReleaseError = require('@semantic-release/error');
-
 const glob = util.promisify(require('glob'));
+const { VERSION_REGEX } = require('./common');
 
 const loadGemspec = async cwd => {
   const gemspecs = await glob('*.gemspec', { cwd });
@@ -23,7 +24,6 @@ Please follow the "[Make your own gem guide](https://guides.rubygems.org/make-yo
   const [gemspec] = gemspecs;
   let gemName = null;
   try {
-    // TODO: Use cwd here instead of the full path?
     const { stdout } = await execa(
       'ruby',
       ['-e', `puts Gem::Specification.load('${gemspec}').name`],
@@ -55,8 +55,7 @@ Please make sure to add a valid \`name\` for your gem in your \`.gemspec\`.
   return { name: gemName, gemspec };
 };
 
-const findVersionFile = async cwd => {
-  // TODO: Should we verify that we can find the version here?
+const verifyVersionFile = async cwd => {
   const versionFiles = await glob('lib/**/version.rb', { cwd });
   if (versionFiles.length !== 1) {
     throw new SemanticReleaseError(
@@ -69,7 +68,21 @@ Please create a \`version.rb\` file with a defined \`VERSION\` constant in your
     );
   }
 
-  return versionFiles[0];
+  const [versionFile] = versionFiles;
+  const fullVersionPath = path.resolve(cwd, versionFile);
+  const versionContents = await readFile(fullVersionPath, 'utf8');
+  if (!VERSION_REGEX.test(versionContents)) {
+    throw new SemanticReleaseError(
+      `Couldn't find a valid version constant defined in \`${versionFile}\`.`,
+      'EINVALIDVERSIONFILE',
+      `Your \`version.rb\` file must define a \`VERSION\` constant.
+
+Please define your gem's version a string constant named \`VERSION\` inside your \`version.rb\` file.
+      `,
+    );
+  }
+
+  return versionFile;
 };
 
 const verifyApiKey = async ({ env, credentialsFile }) => {
@@ -105,7 +118,7 @@ module.exports = async function verify(pluginConfig, { env, cwd }, { credentials
   const { name, gemspec } = await loadGemspec(cwd);
 
   // - Locate version file
-  const versionFile = await findVersionFile(cwd);
+  const versionFile = await verifyVersionFile(cwd);
 
   // - Verify env var
   await verifyApiKey({ env, cwd, credentialsFile });