diff --git a/src/Parser.c b/src/Parser.c
index aee970b..bef70af 100644
--- a/src/Parser.c
+++ b/src/Parser.c
@@ -25,14 +25,49 @@
 #include <Parser.h>
 
 #include <Cytoplasm/Str.h>
+#include <Cytoplasm/Memory.h>
 
 #include <string.h>
+#include <ctype.h>
+
+/* Parse an extended localpart */
+static int
+ParseUserLocalpart(char **str, char **out)
+{
+    char c;
+    char *start;
+    size_t length;
+
+    if (!str || !out)
+    {
+        return 0;
+    }
+    /* An extended localpart contains every ASCII printable character, 
+     * except an ':'. */
+    start = *str;
+    while (isascii((c = (*(*str)++))) && c != ':' && c)
+    {
+        /* Do nothing */
+    }
+    length = (size_t) (*str - start) -1;
+    if (c != ':' || length < 1)
+    {
+        *str = start;
+        return 0;
+    }
+
+    *out = Malloc(length + 1);
+    memcpy(*out, start, length);
+    *out[length] = '\0';
+
+
+    return 1;
+}
 
 int
 ParseCommonID(char *str, CommonID *id)
 {
     char sigil;
-    char *servstart;
 
     if (!str || !id)
     {
@@ -54,17 +89,17 @@ ParseCommonID(char *str, CommonID *id)
         return 0;
     }
     id->sigil = sigil;
-
-    /* Find the position of a ':' if there is one. */
-    if ((servstart = strchr(str, ':')))
-    {
-        id->local   = StrSubstr(str, 1, (char) (servstart - str));
-        id->server  = StrDuplicate(servstart + 1);
-        return 1;
-    }
-    /* Otherwise, just take the rest of the string. */
-    id->local   = StrDuplicate(str + 1) ;
-    id->server  = NULL                  ;
     
+    switch(sigil)
+    {
+        case '@':
+            if (!ParseUserLocalpart(&str, &id->local))
+            {
+                return 0;
+            }
+            /* TODO: Match whenever str is valid. */
+            id->server = StrDuplicate(str);
+            break;
+    }
     return 1;
 }