diff --git a/platform/lang-api/src/com/intellij/psi/codeStyle/CodeStyleSettings.java b/platform/lang-api/src/com/intellij/psi/codeStyle/CodeStyleSettings.java
index 95f733e56ebd..9b8bb18ff196 100644
--- a/platform/lang-api/src/com/intellij/psi/codeStyle/CodeStyleSettings.java
+++ b/platform/lang-api/src/com/intellij/psi/codeStyle/CodeStyleSettings.java
@@ -597,7 +597,9 @@ public class CodeStyleSettings extends CommonCodeStyleSettings implements Clonea
 
     for (final CustomCodeStyleSettings settings : customSettings) {
       final CustomCodeStyleSettings parentCustomSettings = parentSettings.getCustomSettings(settings.getClass());
-      assert parentCustomSettings != null : "Custom settings are null for " + settings.getClass();
+      if (parentCustomSettings == null) {
+        throw new WriteExternalException("Custom settings are null for " + settings.getClass());
+      }
       settings.writeExternal(element, parentCustomSettings);
     }