diff --git a/dlls/msi/source.c b/dlls/msi/source.c
index 11140c48bf9..bdd32444b79 100644
--- a/dlls/msi/source.c
+++ b/dlls/msi/source.c
@@ -589,11 +589,12 @@ UINT WINAPI MsiSourceListAddSourceExW( LPCWSTR szProduct, LPCWSTR szUserSid,
     HKEY typekey;
     UINT rc;
     media_info source_struct;
+    WCHAR squished_pc[GUID_SIZE];
 
     TRACE("%s %s %x %x %s %i\n", debugstr_w(szProduct), debugstr_w(szUserSid),
           dwContext, dwOptions, debugstr_w(szSource), dwIndex);
 
-    if (!szProduct)
+    if (!szProduct || !squash_guid(szProduct, squished_pc))
         return ERROR_INVALID_PARAMETER;
 
     if (!szSource)
diff --git a/dlls/msi/tests/source.c b/dlls/msi/tests/source.c
index aa58c362391..140da845b6c 100644
--- a/dlls/msi/tests/source.c
+++ b/dlls/msi/tests/source.c
@@ -365,27 +365,18 @@ static void test_MsiSourceListAddSourceEx(void)
     /* empty szProductCodeOrPatchCode */
     r = pMsiSourceListAddSourceExA("", usersid, MSIINSTALLCONTEXT_USERUNMANAGED,
                                   MSICODE_PRODUCT | MSISOURCETYPE_URL, "C:\\source", 0);
-    todo_wine
-    {
-        ok(r == ERROR_INVALID_PARAMETER, "Expected ERROR_INVALID_PARAMETER, got %d\n", r);
-    }
+    ok(r == ERROR_INVALID_PARAMETER, "Expected ERROR_INVALID_PARAMETER, got %d\n", r);
 
     /* garbage szProductCodeOrPatchCode */
     r = pMsiSourceListAddSourceExA("garbage", usersid, MSIINSTALLCONTEXT_USERUNMANAGED,
                                   MSICODE_PRODUCT | MSISOURCETYPE_URL, "C:\\source", 0);
-    todo_wine
-    {
-        ok(r == ERROR_INVALID_PARAMETER, "Expected ERROR_INVALID_PARAMETER, got %d\n", r);
-    }
+    ok(r == ERROR_INVALID_PARAMETER, "Expected ERROR_INVALID_PARAMETER, got %d\n", r);
 
     /* guid without brackets */
     r = pMsiSourceListAddSourceExA("51CD2AD5-0482-4C46-8DDD-0ED1022AA1AA", usersid,
                                   MSIINSTALLCONTEXT_USERUNMANAGED,
                                   MSICODE_PRODUCT | MSISOURCETYPE_URL, "C:\\source", 0);
-    todo_wine
-    {
-        ok(r == ERROR_INVALID_PARAMETER, "Expected ERROR_INVALID_PARAMETER, got %d\n", r);
-    }
+    ok(r == ERROR_INVALID_PARAMETER, "Expected ERROR_INVALID_PARAMETER, got %d\n", r);
 
     /* guid with brackets */
     r = pMsiSourceListAddSourceExA("{51CD2AD5-0482-4C46-8DDD-0ED1022AA1AA}", usersid,