diff --git a/lib/util/version.js b/lib/util/version.js
index 4aa472ccaa..6d3587ea7f 100644
--- a/lib/util/version.js
+++ b/lib/util/version.js
@@ -32,7 +32,11 @@ function getReactVersionFromContext(context) {
     if (settingsVersion === 'detect') {
       settingsVersion = detectReactVersion();
     }
-    confVer = settingsVersion;
+    if (typeof settingsVersion !== 'string') {
+      log('Warning: React version specified in eslint-plugin-react-settings must be a string; ' +
+        `got “${typeof settingsVersion}”`);
+    }
+    confVer = String(settingsVersion);
   } else if (!warnedForMissingVersion) {
     log('Warning: React version not specified in eslint-plugin-react settings. ' +
       'See https://github.com/yannickcr/eslint-plugin-react#configuration.');
@@ -46,7 +50,12 @@ function getFlowVersionFromContext(context) {
   let confVer = '999.999.999';
   // .eslintrc shared settings (http://eslint.org/docs/user-guide/configuring#adding-shared-settings)
   if (context.settings.react && context.settings.react.flowVersion) {
-    confVer = context.settings.react.flowVersion;
+    const flowVersion = context.settings.react.flowVersion;
+    if (typeof flowVersion !== 'string') {
+      log('Warning: Flow version specified in eslint-plugin-react-settings must be a string; ' +
+        `got “${typeof flowVersion}”`);
+    }
+    confVer = String(flowVersion);
   } else {
     throw 'Could not retrieve flowVersion from settings';
   }
@@ -54,11 +63,18 @@ function getFlowVersionFromContext(context) {
   return confVer.split('.').map(part => Number(part));
 }
 
+function normalizeParts(parts) {
+  return Array.from({length: 3}, (_, i) => (parts[i] || 0));
+}
+
 function test(context, methodVer, confVer) {
-  methodVer = String(methodVer || '').split('.').map(part => Number(part));
-  const higherMajor = methodVer[0] < confVer[0];
-  const higherMinor = methodVer[0] === confVer[0] && methodVer[1] < confVer[1];
-  const higherOrEqualPatch = methodVer[0] === confVer[0] && methodVer[1] === confVer[1] && methodVer[2] <= confVer[2];
+  const methodVers = normalizeParts(String(methodVer || '').split('.').map(part => Number(part)));
+  const confVers = normalizeParts(confVer);
+  const higherMajor = methodVers[0] < confVers[0];
+  const higherMinor = methodVers[0] === confVers[0] && methodVers[1] < confVers[1];
+  const higherOrEqualPatch = methodVers[0] === confVers[0]
+    && methodVers[1] === confVers[1]
+    && methodVers[2] <= confVers[2];
 
   return higherMajor || higherMinor || higherOrEqualPatch;
 }
diff --git a/tests/util/version.js b/tests/util/version.js
index 5112f8afcd..a4d7733720 100644
--- a/tests/util/version.js
+++ b/tests/util/version.js
@@ -31,4 +31,20 @@ describe('Version', () => {
       assert.equal(versionUtil.testReactVersion(context, '999.999.999'), true);
     });
   });
+
+  describe('non-string version', () => {
+    const context = {settings: {react: {version: 15.0, flowVersion: 1.2}}};
+
+    it('works with react', () => {
+      assert.equal(versionUtil.testReactVersion(context, '0.14.0'), true);
+      assert.equal(versionUtil.testReactVersion(context, '15.0.0'), true);
+      assert.equal(versionUtil.testReactVersion(context, '16.0.0'), false);
+    });
+
+    it('works with flow', () => {
+      assert.equal(versionUtil.testFlowVersion(context, '1.1.0'), true);
+      assert.equal(versionUtil.testFlowVersion(context, '1.2.0'), true);
+      assert.equal(versionUtil.testFlowVersion(context, '1.3.0'), false);
+    });
+  });
 });