diff --git a/src/lint/linter/ArcanistCSSLintLinter.php b/src/lint/linter/ArcanistCSSLintLinter.php
--- a/src/lint/linter/ArcanistCSSLintLinter.php
+++ b/src/lint/linter/ArcanistCSSLintLinter.php
@@ -34,6 +34,17 @@
     return $config->getConfigFromAnySource('lint.csslint.bin', 'csslint');
   }
 
+  public function getVersion() {
+    list($stdout) = execx('%C --version', $this->getExecutableCommand());
+
+    $matches = array();
+    if (preg_match('/^v(?P<version>\d+\.\d+\.\d+)$/', $stdout, $matches)) {
+      return $matches['version'];
+    } else {
+      return false;
+    }
+  }
+
   public function getInstallInstructions() {
     return pht('Install CSSLint using `npm install -g csslint`.');
   }
diff --git a/src/lint/linter/ArcanistExternalLinter.php b/src/lint/linter/ArcanistExternalLinter.php
--- a/src/lint/linter/ArcanistExternalLinter.php
+++ b/src/lint/linter/ArcanistExternalLinter.php
@@ -369,6 +369,21 @@
     return array_merge($mandatory_flags, $flags);
   }
 
+  public function getCacheVersion() {
+    $version = $this->getVersion();
+
+    if ($version) {
+      return $version.'-'.json_encode($this->getCommandFlags());
+    } else {
+      // Either we failed to parse the version number or the `getVersion`
+      // function hasn't been implemented.
+      return json_encode($this->getCommandFlags());
+    }
+  }
+
+  public function getVersion() {
+    return null;
+  }
 
   protected function buildFutures(array $paths) {
     $executable = $this->getExecutableCommand();
diff --git a/src/lint/linter/ArcanistFlake8Linter.php b/src/lint/linter/ArcanistFlake8Linter.php
--- a/src/lint/linter/ArcanistFlake8Linter.php
+++ b/src/lint/linter/ArcanistFlake8Linter.php
@@ -34,6 +34,17 @@
     return 'flake8';
   }
 
+  public function getVersion() {
+    list($stdout) = execx('%C --version', $this->getExecutableCommand());
+
+    $matches = array();
+    if (preg_match('/^(?P<version>\d+\.\d+\.\d+)\b/', $stdout, $matches)) {
+      return $matches['version'];
+    } else {
+      return false;
+    }
+  }
+
   public function getInstallInstructions() {
     return pht('Install flake8 using `easy_install flake8`.');
   }
diff --git a/src/lint/linter/ArcanistJSHintLinter.php b/src/lint/linter/ArcanistJSHintLinter.php
--- a/src/lint/linter/ArcanistJSHintLinter.php
+++ b/src/lint/linter/ArcanistJSHintLinter.php
@@ -35,18 +35,16 @@
     }
   }
 
-  public function getCacheVersion() {
+  public function getVersion() {
     list($stdout) = execx('%C --version', $this->getExecutableCommand());
 
-    // Extract version number from standard output.
     $matches = array();
-    if (preg_match('/^jshint v(\d+\.\d+\.\d+)$/', $stdout, $matches)) {
-      $version = $matches[1];
+    $regex = '/^jshint v(?P<version>\d+\.\d+\.\d+)$/';
+    if (preg_match($regex, $stdout, $matches)) {
+      return $matches['version'];
     } else {
-      $version = md5($stdout);
+      return false;
     }
-
-    return $version . '-' . md5(json_encode($this->getCommandFlags()));
   }
 
   public function getInstallInstructions() {
diff --git a/src/lint/linter/ArcanistPEP8Linter.php b/src/lint/linter/ArcanistPEP8Linter.php
--- a/src/lint/linter/ArcanistPEP8Linter.php
+++ b/src/lint/linter/ArcanistPEP8Linter.php
@@ -15,11 +15,6 @@
     return 'pep8';
   }
 
-  public function getCacheVersion() {
-    list($stdout) = execx('%C --version', $this->getExecutableCommand());
-    return $stdout.implode(' ', $this->getCommandFlags());
-  }
-
   public function getDefaultFlags() {
     // TODO: Warn that all of this is deprecated.
     $config = $this->getEngine()->getConfigurationManager();
@@ -55,6 +50,17 @@
     return $arc_root.'/externals/pep8/pep8.py';
   }
 
+  public function getVersion() {
+    list($stdout) = execx('%C --version', $this->getExecutableCommand());
+
+    $matches = array();
+    if (preg_match('/^(?P<version>\d+\.\d+\.\d+)$/', $stdout, $matches)) {
+      return $matches['version'];
+    } else {
+      return false;
+    }
+  }
+
   public function getInstallInstructions() {
     return pht('Install PEP8 using `easy_install pep8`.');
   }
diff --git a/src/lint/linter/ArcanistPhpcsLinter.php b/src/lint/linter/ArcanistPhpcsLinter.php
--- a/src/lint/linter/ArcanistPhpcsLinter.php
+++ b/src/lint/linter/ArcanistPhpcsLinter.php
@@ -58,6 +58,18 @@
     return $config->getConfigFromAnySource('lint.phpcs.bin', 'phpcs');
   }
 
+  public function getVersion() {
+    list($stdout) = execx('%C --version', $this->getExecutableCommand());
+
+    $matches = array();
+    $regex = '/^PHP_CodeSniffer version (?P<version>\d+\.\d+\.\d+)\b/';
+    if (preg_match($regex, $stdout, $matches)) {
+      return $matches['version'];
+    } else {
+      return false;
+    }
+  }
+
   public function shouldExpectCommandErrors() {
     return true;
   }
diff --git a/src/lint/linter/ArcanistRubyLinter.php b/src/lint/linter/ArcanistRubyLinter.php
--- a/src/lint/linter/ArcanistRubyLinter.php
+++ b/src/lint/linter/ArcanistRubyLinter.php
@@ -26,6 +26,18 @@
     return 'ruby';
   }
 
+  public function getVersion() {
+    list($stdout) = execx('%C --version', $this->getExecutableCommand());
+
+    $matches = array();
+    $regex = '/^ruby (?P<version>\d+\.\d+\.\d+)p\d+/';
+    if (preg_match($regex, $stdout, $matches)) {
+      return $matches['version'];
+    } else {
+      return false;
+    }
+  }
+
   public function getInstallInstructions() {
     return pht('Install `ruby` from <http://www.ruby-lang.org/>.');
   }