diff --git a/anonstream/captcha.py b/anonstream/captcha.py
index fb1b0af..49ffd28 100644
--- a/anonstream/captcha.py
+++ b/anonstream/captcha.py
@@ -33,8 +33,6 @@ def get_random_captcha_digest():
         solution = generate_random_captcha_solution()
         digest = generate_captcha_digest(CAPTCHA_SIGNER, salt, solution)
         CAPTCHAS[digest] = {'solution': solution}
-        while len(CAPTCHAS) >= CONFIG['MAX_CAPTCHAS']:
-            CAPTCHAS.popitem(last=False)
 
     return digest
 
diff --git a/anonstream/config.py b/anonstream/config.py
index 346f2c6..755d84e 100644
--- a/anonstream/config.py
+++ b/anonstream/config.py
@@ -84,6 +84,7 @@ def toml_to_flask_section_names(config):
 def toml_to_flask_section_memory(config):
     cfg = config['memory']
     assert cfg['states'] >= 0
+    assert cfg['captchas'] >= 1
     assert cfg['failures'] >= 0
     assert cfg['chat_scrollback'] >= 0
     assert cfg['chat_messages'] >= cfg['chat_scrollback']