diff --git a/dlls/msi/source.c b/dlls/msi/source.c
index 2d33bc1be9..d1845379a5 100644
--- a/dlls/msi/source.c
+++ b/dlls/msi/source.c
@@ -603,7 +603,7 @@ UINT WINAPI MsiSourceListAddSourceExW( LPCWSTR szProduct, LPCWSTR szUserSid,
     if (!szProduct || !squash_guid(szProduct, squished_pc))
         return ERROR_INVALID_PARAMETER;
 
-    if (!szSource)
+    if (!szSource || !*szSource)
         return ERROR_INVALID_PARAMETER;
 
     if (dwOptions & MSICODE_PATCH)
diff --git a/dlls/msi/tests/source.c b/dlls/msi/tests/source.c
index 8fccfbe053..d81a29aeea 100644
--- a/dlls/msi/tests/source.c
+++ b/dlls/msi/tests/source.c
@@ -617,10 +617,7 @@ static void test_MsiSourceListAddSourceEx(void)
     r = pMsiSourceListAddSourceExA(prodcode, usersid,
                                   MSIINSTALLCONTEXT_USERUNMANAGED,
                                   MSISOURCETYPE_URL, "", 1);
-    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);
 
     /* MSIINSTALLCONTEXT_USERMANAGED, non-NULL szUserSid */