diff --git a/openid/src/main/java/org/springframework/security/openid/OpenIDAuthenticationFilter.java b/openid/src/main/java/org/springframework/security/openid/OpenIDAuthenticationFilter.java
index 99bd8068de..503ef6e434 100644
--- a/openid/src/main/java/org/springframework/security/openid/OpenIDAuthenticationFilter.java
+++ b/openid/src/main/java/org/springframework/security/openid/OpenIDAuthenticationFilter.java
@@ -27,8 +27,10 @@ import org.springframework.util.StringUtils;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;
+import java.io.UnsupportedEncodingException;
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.net.URLEncoder;
 import java.util.*;
 
 
@@ -186,32 +188,37 @@ public class OpenIDAuthenticationFilter extends AbstractAuthenticationProcessing
      * @return The <tt>return_to</tt> URL.
      */
     protected String buildReturnToUrl(HttpServletRequest request) {
-        StringBuffer sb = request.getRequestURL();
-
-        Iterator<String> iterator = returnToUrlParameters.iterator();
-        boolean isFirst = true;
-
-        while (iterator.hasNext()) {
-            String name = iterator.next();
-            // Assume for simplicity that there is only one value
-            String value = request.getParameter(name);
-
-            if (value == null) {
-                continue;
-            }
-
-            if (isFirst) {
-                sb.append("?");
-                isFirst = false;
-            }
-            sb.append(name).append("=").append(value);
-
-            if (iterator.hasNext()) {
-                sb.append("&");
+        try {
+            StringBuffer sb = request.getRequestURL();
+    
+            Iterator<String> iterator = returnToUrlParameters.iterator();
+            boolean isFirst = true;
+    
+            while (iterator.hasNext()) {
+                String name = iterator.next();
+                // Assume for simplicity that there is only one value
+                String value = request.getParameter(name);
+    
+                if (value == null) {
+                    continue;
+                }
+    
+                if (isFirst) {
+                    sb.append("?");
+                    isFirst = false;
+                }
+                sb.append(URLEncoder.encode(name, "UTF-8")).append("=").append(URLEncoder.encode(value, "UTF-8"));
+    
+                if (iterator.hasNext()) {
+                    sb.append("&");
+                }
             }
+            return sb.toString();
+        } catch(UnsupportedEncodingException e) {
+            Error err = new AssertionError("The Java platform guarantees UTF-8 support, but it seemingly is not present.");
+            err.initCause(e);
+            throw err;
         }
-
-        return sb.toString();
     }
 
     /**
diff --git a/openid/src/test/java/org/springframework/security/openid/OpenIDAuthenticationFilterTests.java b/openid/src/test/java/org/springframework/security/openid/OpenIDAuthenticationFilterTests.java
index 54efad432a..80adce08b3 100644
--- a/openid/src/test/java/org/springframework/security/openid/OpenIDAuthenticationFilterTests.java
+++ b/openid/src/test/java/org/springframework/security/openid/OpenIDAuthenticationFilterTests.java
@@ -4,6 +4,9 @@ import static org.junit.Assert.assertEquals;
 import static org.mockito.Matchers.any;
 import static org.mockito.Mockito.*;
 
+import java.net.URI;
+import java.util.Collections;
+
 import javax.servlet.FilterChain;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -63,4 +66,35 @@ public class OpenIDAuthenticationFilterTests {
         // Filter chain shouldn't proceed
         verify(fc, never()).doFilter(any(HttpServletRequest.class), any(HttpServletResponse.class));
     }
+    
+    /**
+     * Tests that the filter encodes any query parameters on the return_to URL.
+     */
+    @Test
+    public void encodesUrlParameters() throws Exception {
+        // Arbitrary parameter name and value that will both need to be encoded:
+        String paramName = "foo&bar";
+        String paramValue = "http://example.com/path?a=b&c=d";
+        MockHttpServletRequest req = new MockHttpServletRequest("GET", REQUEST_PATH);
+        req.addParameter(paramName, paramValue);
+        filter.setReturnToUrlParameters(Collections.singleton(paramName));
+        
+        URI returnTo = new URI(filter.buildReturnToUrl(req));
+        String query = returnTo.getRawQuery();
+        assertEquals(1, count(query, '='));
+        assertEquals(0, count(query, '&'));
+    }
+    
+    /**
+     * Counts the number of occurrences of {@code c} in {@code s}.
+     */
+    private static int count(String s, char c) {
+        int count = 0;
+        for(char ch : s.toCharArray()) {
+            if(c == ch) {
+                count += 1;
+            }
+        }
+        return count;
+    }
 }