diff --git a/engine/String.cpp b/engine/String.cpp
index e519f2d9..a81277e6 100644
--- a/engine/String.cpp
+++ b/engine/String.cpp
@@ -1350,12 +1350,11 @@ String String::uriUnescape(const char* str, int* errptr)
     return s;
 }
 
-unsigned int String::hash(const char* value)
+unsigned int String::hash(const char* value, unsigned int h)
 {
     if (!value)
 	return 0;
 
-    unsigned int h = 0;
     // sdbm hash algorithm, hash(i) = hash(i-1) * 65599 + str[i]
     while (unsigned char c = (unsigned char) *value++)
 	h = (h << 6) + (h << 16) - h + c;
diff --git a/yateclass.h b/yateclass.h
index 4f0e9112..bb8e9cdb 100644
--- a/yateclass.h
+++ b/yateclass.h
@@ -1994,9 +1994,10 @@ public:
     /**
      * Get the hash of an arbitrary string.
      * @param value C string to hash
+     * @param h Old hash value for incremental hashing
      * @return The hash of the string.
      */
-    static unsigned int hash(const char* value);
+    static unsigned int hash(const char* value, unsigned int h = 0);
 
     /**
      * Clear the string and free the memory