diff --git a/dist/index.js b/dist/index.js
index 0f6585b..26a2787 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -26067,9 +26067,13 @@ function requestedVersionFor(tool, version, originListing, mirrors) {
   )
 }
 
+const knownBranches = ['main', 'master', 'maint']
+const nonSpecificVersions = ['nightly', 'latest']
+
 async function getElixirVersion(exSpec0, otpVersion0) {
   const otpVersion = otpVersion0.match(/^(?:OTP-)?(.+)$/)[1]
-  let otpVersionMajor = otpVersion.match(/^([^.]+).*$/)[1]
+  const regex = `^(\\d{1,3}|${knownBranches.join('|')}|${nonSpecificVersions.join('|')})?.*$`
+  let otpVersionMajor = otpVersion.match(new RegExp(regex))[1]
 
   const otpSuffix = /-otp-(\d+)/
   const userSuppliedOtp = exSpec0.match(otpSuffix)?.[1] ?? null
@@ -26316,7 +26320,9 @@ function gt(left, right) {
 
 function validVersion(v) {
   return (
-    v.match(/main|master|nightly|latest/g) == null &&
+    v.match(
+      new RegExp(`${knownBranches.join('|')}|${nonSpecificVersions.join('|')}`),
+    ) == null &&
     !v.startsWith('a') &&
     !v.startsWith('b')
   )
@@ -26435,8 +26441,6 @@ function isRC(ver) {
   return ver.match(xyzAbcVersion('^', '(?:-rc\\.?\\d+)'))
 }
 
-const knownBranches = ['main', 'master', 'maint']
-
 function isKnownBranch(ver) {
   return knownBranches.includes(ver)
 }
diff --git a/src/setup-beam.js b/src/setup-beam.js
index 926e0c5..af3961c 100644
--- a/src/setup-beam.js
+++ b/src/setup-beam.js
@@ -192,9 +192,13 @@ function requestedVersionFor(tool, version, originListing, mirrors) {
   )
 }
 
+const knownBranches = ['main', 'master', 'maint']
+const nonSpecificVersions = ['nightly', 'latest']
+
 async function getElixirVersion(exSpec0, otpVersion0) {
   const otpVersion = otpVersion0.match(/^(?:OTP-)?(.+)$/)[1]
-  let otpVersionMajor = otpVersion.match(/^([^.]+).*$/)[1]
+  const regex = `^(\\d{1,3}|${knownBranches.join('|')}|${nonSpecificVersions.join('|')})?.*$`
+  let otpVersionMajor = otpVersion.match(new RegExp(regex))[1]
 
   const otpSuffix = /-otp-(\d+)/
   const userSuppliedOtp = exSpec0.match(otpSuffix)?.[1] ?? null
@@ -441,7 +445,9 @@ function gt(left, right) {
 
 function validVersion(v) {
   return (
-    v.match(/main|master|nightly|latest/g) == null &&
+    v.match(
+      new RegExp(`${knownBranches.join('|')}|${nonSpecificVersions.join('|')}`),
+    ) == null &&
     !v.startsWith('a') &&
     !v.startsWith('b')
   )
@@ -560,8 +566,6 @@ function isRC(ver) {
   return ver.match(xyzAbcVersion('^', '(?:-rc\\.?\\d+)'))
 }
 
-const knownBranches = ['main', 'master', 'maint']
-
 function isKnownBranch(ver) {
   return knownBranches.includes(ver)
 }