diff --git a/src/Lib/IO.php b/src/Lib/IO.php
index a7842dd..3da2abd 100644
--- a/src/Lib/IO.php
+++ b/src/Lib/IO.php
@@ -67,21 +67,22 @@ class IO implements ILib
         ));
 
         // Readline support
+        if (extension_loaded('readline')) {
+            $env->set('readline', new CoreFunc('readline', 'Read line of user input.', 0, 1,
+                fn ($prompt = null) => readline($prompt)
+            ));
 
-        $env->set('readline', new CoreFunc('readline', 'Read line of user input.', 0, 1,
-            fn ($prompt = null) => readline($prompt)
-        ));
+            $env->set('readline-add', new CoreFunc('readline-add', 'Add new line of input to history.', 1, 1,
+                fn (string $line) => readline_add_history($line)
+            ));
 
-        $env->set('readline-add', new CoreFunc('readline-add', 'Add new line of input to history.', 1, 1,
-            fn (string $line) => readline_add_history($line)
-        ));
+            $env->set('readline-load', new CoreFunc('readline-load', 'Load the history for readline from a file.', 1, 1,
+                fn (string $file) => readline_read_history($file)
+            ));
 
-        $env->set('readline-load', new CoreFunc('readline-load', 'Load the history for readline from a file.', 1, 1,
-            fn (string $file) => readline_read_history($file)
-        ));
-
-        $env->set('readline-save', new CoreFunc('readline-save', 'Save the readline history into a file.', 1, 1,
-            fn (string $file) => readline_write_history($file)
-        ));
+            $env->set('readline-save', new CoreFunc('readline-save', 'Save the readline history into a file.', 1, 1,
+                fn (string $file) => readline_write_history($file)
+            ));
+        }
     }
 }
diff --git a/src/LispFactory.php b/src/LispFactory.php
index e1d8de5..5114143 100644
--- a/src/LispFactory.php
+++ b/src/LispFactory.php
@@ -19,17 +19,25 @@ class LispFactory
         // Register core libraries
         (new Lib\Collections())->register($env);
         (new Lib\Compare())->register($env);
-        (new Lib\Json())->register($env);
+        if (extension_loaded('json')) {
+            (new Lib\Json())->register($env);
+        }
         (new Lib\Math())->register($env);
-        (new Lib\Regex())->register($env);
+        if (extension_loaded('pcre')) {
+            (new Lib\Regex())->register($env);
+        }
         (new Lib\Strings())->register($env);
         (new Lib\Time())->register($env);
         (new Lib\Types())->register($env);
 
         // Register unsafe libraries if not in safe-mode
         if (!$safemode) {
-            (new Lib\Database())->register($env);
-            (new Lib\Http())->register($env);
+            if (extension_loaded('PDO')) {
+                (new Lib\Database())->register($env);
+            }
+            if (extension_loaded('curl')) {
+                (new Lib\Http())->register($env);
+            }
             (new Lib\IO())->register($env);
         }