diff --git a/src/next-version.mjs b/src/next-version.mjs
index fc0fc60..f49319e 100644
--- a/src/next-version.mjs
+++ b/src/next-version.mjs
@@ -22,6 +22,11 @@ import {
  *    other prerelease ID with a 'pretype' increment will result in undefined results
  */
 const nextVersion = ({ currVer, increment }) => {
+  if (!semver.valid(currVer)) {
+    const msg = `Invalid version '${currVer}'` + (semver.validRange(currVer) ? '; range not allowed.' : '.')
+    throw createError.BadRequest(msg)
+  }
+
   if (increment !== undefined && !STANDARD_INCREMENTS.includes(increment)) {
     throw createError.BadRequest(`Invalid increment '${increment}' specified.`)
   }
@@ -76,10 +81,10 @@ const nextVersion = ({ currVer, increment }) => {
   }
   else if (STANDARD_RELEASE_NAMES.includes(increment)) {
     if (increment === 'gold') {
-      nextVer = currVer.replace(/^([\d.Z]+)-(?:alpha|beta|rc)(?:\.\d+)?/, '$1')
+      nextVer = currVer.replace(/^([\d.]+)-(?:alpha|beta|rc)(?:\.\d+)?/, '$1')
     }
     else {
-      nextVer = currVer.replace(/^([\d.Z-]+)(?:alpha|beta|rc)(?:\.\d+)?/, `$1${increment}.0`)
+      nextVer = currVer.replace(/^([\d.]+)-(?:alpha|beta|rc)(?:\.\d+)?/, `$1-${increment}.0`)
     }
 
     return nextVer
diff --git a/src/test/next-version.test.js b/src/test/next-version.test.js
index 765e8d0..659d9f0 100644
--- a/src/test/next-version.test.js
+++ b/src/test/next-version.test.js
@@ -64,4 +64,7 @@ describe('nextVersion', () => {
     const currVer = `1.0.0-${currPrerelease}`
     expect(() => ver.version({ currVer, increment : 'prerelease' }))
   })
+
+  test.each(['1.0.x', '^1.0.0', '1.0.0 - 1.x', '~1.0.0'])('raises except on range input %s', (currVer) =>
+    expect(() => ver.nextVersion({ currVer, increment : 'prerelease' })).toThrow(/range not allowed/i))
 })