diff --git a/dlls/msacm32/stream.c b/dlls/msacm32/stream.c
index bdfc3ccf2aa..b380b461ad3 100644
--- a/dlls/msacm32/stream.c
+++ b/dlls/msacm32/stream.c
@@ -302,14 +302,16 @@ MMRESULT WINAPI acmStreamPrepareHeader(HACMSTREAM has, PACMSTREAMHEADER pash,
 
     if ((was = ACM_GetStream(has)) == NULL) {
         WARN("invalid handle\n");
-	return MMSYSERR_INVALHANDLE;
+        return MMSYSERR_INVALHANDLE;
     }
     if (!pash || pash->cbStruct < sizeof(ACMSTREAMHEADER)) {
         WARN("invalid parameter\n");
-	return MMSYSERR_INVALPARAM;
+        return MMSYSERR_INVALPARAM;
+    }
+    if (fdwPrepare) {
+        WARN("invalid use of reserved parameter\n");
+        return MMSYSERR_INVALFLAG;
     }
-    if (fdwPrepare)
-	ret = MMSYSERR_INVALFLAG;
 
     /* Note: the ACMSTREAMHEADER and ACMDRVSTREAMHEADER structs are of same
      * size. some fields are private to msacm internals, and are exposed
diff --git a/dlls/msacm32/tests/msacm.c b/dlls/msacm32/tests/msacm.c
index 812a1bbf3a5..06e530b6293 100644
--- a/dlls/msacm32/tests/msacm.c
+++ b/dlls/msacm32/tests/msacm.c
@@ -601,7 +601,6 @@ todo_wine
 
     hdr.cbSrcLength = src->wfx.nBlockAlign;
     mr = acmStreamPrepareHeader(has, &hdr, 1); /* invalid use of reserved parameter */
-todo_wine
     ok(mr == MMSYSERR_INVALFLAG, "expected 0x0a, got 0x%x\n", mr);
 
     mr = acmStreamPrepareHeader(has, &hdr, 0);