diff --git a/CHANGELOG.md b/CHANGELOG.md
index a90058ab..ea3a9c3e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,8 @@ FlatLaf Change Log
     "Material Theme UI Lite" themes; issue #667; regression in FlatLaf 3.1).
   - Fixed too large tree row height in "Carbon", "Dark Purple", "Gray",
     "Material Design Dark", "Monokai Pro", "One Dark" and "Spacegray" themes.
+- Native libraries: Fixed `IllegalArgumentException: URI scheme is not "file"`
+  when using FlatLaf in WebStart. (issue #668; regression in FlatLaf 3.1)
 
 
 ## 3.1
diff --git a/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatNativeLibrary.java b/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatNativeLibrary.java
index 7fef79b5..f9daf494 100644
--- a/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatNativeLibrary.java
+++ b/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatNativeLibrary.java
@@ -18,6 +18,7 @@ package com.formdev.flatlaf.ui;
 
 import java.io.File;
 import java.net.URL;
+import java.security.CodeSource;
 import com.formdev.flatlaf.FlatSystemProperties;
 import com.formdev.flatlaf.util.LoggingFacade;
 import com.formdev.flatlaf.util.NativeLibrary;
@@ -128,10 +129,15 @@ class FlatNativeLibrary
 	private static File findLibraryBesideJar( String classifier, String ext ) {
 		try {
 			// get location of FlatLaf jar
-			URL jarUrl = FlatNativeLibrary.class.getProtectionDomain().getCodeSource().getLocation();
+			CodeSource codeSource = FlatNativeLibrary.class.getProtectionDomain().getCodeSource();
+			URL jarUrl = (codeSource != null) ? codeSource.getLocation() : null;
 			if( jarUrl == null )
 				return null;
 
+			// if url is not a file, then we're running in a special environment (e.g. WebStart)
+			if( !"file".equals( jarUrl.getProtocol() ) )
+				return null;
+
 			File jarFile = new File( jarUrl.toURI() );
 
 			// if jarFile is a directory, then we're in a development environment