diff --git a/dlls/dsound/tests/ds3d.c b/dlls/dsound/tests/ds3d.c
index 54b50e25741..4f8ec8f2f18 100644
--- a/dlls/dsound/tests/ds3d.c
+++ b/dlls/dsound/tests/ds3d.c
@@ -420,6 +420,7 @@ void test_buffer(LPDIRECTSOUND dso, LPDIRECTSOUNDBUFFER *dsbo,
            "    buffer size changed after SetFormat() - "
            "previous size was %u, current size is %u\n",
            dsbcaps.dwBufferBytes, new_dsbcaps.dwBufferBytes);
+        dsbcaps.dwBufferBytes = new_dsbcaps.dwBufferBytes;
 
         /* Check for primary buffer flags change */
         ok(new_dsbcaps.dwFlags == dsbcaps.dwFlags,
diff --git a/dlls/dsound/tests/ds3d8.c b/dlls/dsound/tests/ds3d8.c
index 00c0ef7186b..cddcf70a056 100644
--- a/dlls/dsound/tests/ds3d8.c
+++ b/dlls/dsound/tests/ds3d8.c
@@ -307,6 +307,7 @@ void test_buffer8(LPDIRECTSOUND8 dso, LPDIRECTSOUNDBUFFER * dsbo,
            "    buffer size changed after SetFormat() - "
            "previous size was %u, current size is %u\n",
            dsbcaps.dwBufferBytes, new_dsbcaps.dwBufferBytes);
+        dsbcaps.dwBufferBytes = new_dsbcaps.dwBufferBytes;
 
         /* Check for primary buffer flags change */
         ok(new_dsbcaps.dwFlags == dsbcaps.dwFlags,