diff --git a/src/Composer/Autoload/ClassLoader.php b/src/Composer/Autoload/ClassLoader.php
index 95f7e0978..fce8549f0 100644
--- a/src/Composer/Autoload/ClassLoader.php
+++ b/src/Composer/Autoload/ClassLoader.php
@@ -279,7 +279,7 @@ class ClassLoader
      */
     public function setApcuPrefix($apcuPrefix)
     {
-        $this->apcuPrefix = function_exists('apcu_fetch') && ini_get('apc.enabled') ? $apcuPrefix : null;
+        $this->apcuPrefix = function_exists('apcu_fetch') && filter_var(ini_get('apc.enabled'), FILTER_VALIDATE_BOOLEAN) ? $apcuPrefix : null;
     }
 
     /**
diff --git a/src/Composer/Command/DiagnoseCommand.php b/src/Composer/Command/DiagnoseCommand.php
index 3efb34973..3cb783b3b 100644
--- a/src/Composer/Command/DiagnoseCommand.php
+++ b/src/Composer/Command/DiagnoseCommand.php
@@ -481,7 +481,7 @@ EOT
             $errors['iconv_mbstring'] = true;
         }
 
-        if (!ini_get('allow_url_fopen')) {
+        if (!filter_var(ini_get('allow_url_fopen'), FILTER_VALIDATE_BOOLEAN)) {
             $errors['allow_url_fopen'] = true;
         }
 
@@ -505,7 +505,7 @@ EOT
             $warnings['openssl_version'] = true;
         }
 
-        if (!defined('HHVM_VERSION') && !extension_loaded('apcu') && ini_get('apc.enable_cli')) {
+        if (!defined('HHVM_VERSION') && !extension_loaded('apcu') && filter_var(ini_get('apc.enable_cli'), FILTER_VALIDATE_BOOLEAN)) {
             $warnings['apc_cli'] = true;
         }
 
@@ -528,7 +528,7 @@ EOT
             }
         }
 
-        if (ini_get('xdebug.profiler_enabled')) {
+        if (filter_var(ini_get('xdebug.profiler_enabled'), FILTER_VALIDATE_BOOLEAN)) {
             $warnings['xdebug_profile'] = true;
         } elseif (extension_loaded('xdebug')) {
             $warnings['xdebug_loaded'] = true;
diff --git a/src/Composer/Compiler.php b/src/Composer/Compiler.php
index 4064b20b5..27b1f4816 100644
--- a/src/Composer/Compiler.php
+++ b/src/Composer/Compiler.php
@@ -255,7 +255,7 @@ class Compiler
  */
 
 // Avoid APC causing random fatal errors per https://github.com/composer/composer/issues/264
-if (extension_loaded('apc') && ini_get('apc.enable_cli') && ini_get('apc.cache_by_default')) {
+if (extension_loaded('apc') && filter_var(ini_get('apc.enable_cli'), FILTER_VALIDATE_BOOLEAN) && filter_var(ini_get('apc.cache_by_default'), FILTER_VALIDATE_BOOLEAN)) {
     if (version_compare(phpversion('apc'), '3.0.12', '>=')) {
         ini_set('apc.cache_by_default', 0);
     } else {
diff --git a/src/Composer/Util/ErrorHandler.php b/src/Composer/Util/ErrorHandler.php
index 925cab74c..83e6b5ede 100644
--- a/src/Composer/Util/ErrorHandler.php
+++ b/src/Composer/Util/ErrorHandler.php
@@ -41,7 +41,7 @@ class ErrorHandler
             return;
         }
 
-        if (ini_get('xdebug.scream')) {
+        if (filter_var(ini_get('xdebug.scream'), FILTER_VALIDATE_BOOLEAN)) {
             $message .= "\n\nWarning: You have xdebug.scream enabled, the warning above may be".
             "\na legitimately suppressed error that you were not supposed to see.";
         }
diff --git a/src/Composer/Util/RemoteFilesystem.php b/src/Composer/Util/RemoteFilesystem.php
index def4091a6..39f049cbe 100644
--- a/src/Composer/Util/RemoteFilesystem.php
+++ b/src/Composer/Util/RemoteFilesystem.php
@@ -364,7 +364,7 @@ class RemoteFilesystem
             }
             $result = false;
         }
-        if ($errorMessage && !ini_get('allow_url_fopen')) {
+        if ($errorMessage && !filter_var(ini_get('allow_url_fopen'), FILTER_VALIDATE_BOOLEAN)) {
             $errorMessage = 'allow_url_fopen must be enabled in php.ini ('.$errorMessage.')';
         }
         restore_error_handler();