diff --git a/classlib/src/main/java/org/teavm/classlib/java/net/TURL.java b/classlib/src/main/java/org/teavm/classlib/java/net/TURL.java
index 0aba53fa2..fe3086bd7 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/net/TURL.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/net/TURL.java
@@ -72,7 +72,7 @@ public final class TURL implements Serializable {
             throw new TMalformedURLException(e.toString());
         }
         int startIPv6Addr = spec.indexOf('[');
-        if (index >= 0) {
+        if (index > 0) {
             if (startIPv6Addr == -1 || index < startIPv6Addr) {
                 protocol = spec.substring(0, index);
                 // According to RFC 2396 scheme part should match
diff --git a/tests/src/test/java/org/teavm/classlib/java/net/URLTest.java b/tests/src/test/java/org/teavm/classlib/java/net/URLTest.java
index 1768a5da8..5a40be35d 100644
--- a/tests/src/test/java/org/teavm/classlib/java/net/URLTest.java
+++ b/tests/src/test/java/org/teavm/classlib/java/net/URLTest.java
@@ -228,6 +228,15 @@ public class URLTest {
         } catch (MalformedURLException e) {
             fail("Unexpected exception (jar protocol, relative path)" + e);
         }
+
+        // no protocol
+        caught = false;
+        try {
+            u = new URL(":");
+        } catch (MalformedURLException e) {
+            caught = true;
+        }
+        assertTrue("7 Failed to throw MalformedURLException", caught);
     }
 
     @Test