diff --git a/dlls/winmm/waveform.c b/dlls/winmm/waveform.c
index ecffa700662..66444ee82dc 100644
--- a/dlls/winmm/waveform.c
+++ b/dlls/winmm/waveform.c
@@ -183,7 +183,7 @@ typedef struct _WINMM_QueryInterfaceInfo {
     BOOL is_out;
     UINT index;
     WCHAR *str;
-    UINT *len_bytes;
+    ULONG *len_bytes;
 } WINMM_QueryInterfaceInfo;
 
 static LRESULT WOD_Open(WINMM_OpenInfo *info);
@@ -1771,7 +1771,8 @@ exit:
 
 static void WID_PullACMData(WINMM_Device *device)
 {
-    UINT32 packet, packet_bytes;
+    UINT32 packet;
+    DWORD packet_bytes;
     DWORD flags;
     BYTE *data;
     WAVEHDR *queue;