Index: jaxrs/resteasy-jaxrs/src/main/java/org/jboss/resteasy/specimpl/UriBuilderImpl.java
===================================================================
--- jaxrs/resteasy-jaxrs/src/main/java/org/jboss/resteasy/specimpl/UriBuilderImpl.java	(revision 1271)
+++ jaxrs/resteasy-jaxrs/src/main/java/org/jboss/resteasy/specimpl/UriBuilderImpl.java	(revision )
@@ -418,14 +418,27 @@
          if (!param.equals(name)) continue;
          if (!isEncoded)
          {
+            if (matcher.groupCount() == 2)
+            {
-            value = Encode.encodePath(value);
-         }
-         else
-         {
+               value = Encode.encodePath(value);
+            }
+            else
+            {
+               value = Encode.encodePathSegment(value);
+            }
+         }
+         else
+         {
             value = Encode.encodeNonCodes(value);
          }
          // if there is a $ then we must backslash it or it will screw up regex group substitution
          value = value.replace("$", "\\$");
+         if(matcher.groupCount() == 2){
+            String pattern = matcher.group(2).substring(1);
+            if(!pattern.matches(value)){
+               throw new IllegalArgumentException("The parameter value: " + value + " doesn't match the given pattern: " + pattern);
+            }
+         }
          matcher.appendReplacement(buffer, value);
       }
       matcher.appendTail(buffer);