diff --git a/reactos/dll/win32/advapi32/sec/sid.c b/reactos/dll/win32/advapi32/sec/sid.c
index 6dac3dac683..ed466a58914 100644
--- a/reactos/dll/win32/advapi32/sec/sid.c
+++ b/reactos/dll/win32/advapi32/sec/sid.c
@@ -805,6 +805,9 @@ static BOOL ParseStringSidToSid(LPCWSTR StringSid, PSID pSid, LPDWORD cBytes)
         return FALSE;
     }
 
+    while (*StringSid == ' ')
+        StringSid++;
+
     *cBytes = ComputeStringSidSize(StringSid);
     if (!pisid) /* Simply compute the size */
     {