diff --git a/dlls/ntdll/tests/info.c b/dlls/ntdll/tests/info.c
index 6e3851ddeed..f09acc9bc74 100644
--- a/dlls/ntdll/tests/info.c
+++ b/dlls/ntdll/tests/info.c
@@ -124,18 +124,22 @@ static void test_query_performance(void)
     ULONG FullLength;
     ULONG ReturnLength;
     SYSTEM_PERFORMANCE_INFORMATION spi;
-    BYTE Buffer[sizeof(SYSTEM_PERFORMANCE_INFORMATION) + 2];
+    struct SPI_PLUS_EXTRA
+    {
+      SYSTEM_PERFORMANCE_INFORMATION spi;
+      BYTE extra[2];
+    } spi_plus_extra;
 
-    status = pNtQuerySystemInformation(SystemPerformanceInformation, Buffer, 0, &FullLength);
+    status = pNtQuerySystemInformation(SystemPerformanceInformation, &spi, 0, &FullLength);
     ok( status == STATUS_INFO_LENGTH_MISMATCH, "Expected STATUS_INFO_LENGTH_MISMATCH, got %08x\n", status);
 
-    status = pNtQuerySystemInformation(SystemPerformanceInformation, Buffer, sizeof(spi), &ReturnLength);
+    status = pNtQuerySystemInformation(SystemPerformanceInformation, &spi, sizeof(spi), &ReturnLength);
     ok( status == STATUS_SUCCESS, "Expected STATUS_SUCCESS, got %08x\n", status);
     ok( sizeof(spi) == ReturnLength, "Inconsistent length %d\n", ReturnLength);
 
-    status = pNtQuerySystemInformation(SystemPerformanceInformation, &Buffer, sizeof(Buffer), &ReturnLength);
+    status = pNtQuerySystemInformation(SystemPerformanceInformation, &spi_plus_extra, sizeof(spi_plus_extra), &ReturnLength);
     ok( status == STATUS_SUCCESS, "Expected STATUS_SUCCESS, got %08x\n", status);
-    ok( ReturnLength == min(FullLength, sizeof(Buffer)), "Inconsistent length %d\n", ReturnLength);
+    ok( ReturnLength == min(FullLength, sizeof(spi_plus_extra)), "Inconsistent length %d\n", ReturnLength);
 
     /* Not return values yet, as struct members are unknown */
 }