diff --git a/zsnes/src/cpu/dspproc.asm b/zsnes/src/cpu/dspproc.asm
index f7eb78c6..c421d1eb 100644
--- a/zsnes/src/cpu/dspproc.asm
+++ b/zsnes/src/cpu/dspproc.asm
@@ -1720,12 +1720,14 @@ NEWSYM LPFsample2, dd 0
     mov edx,eax
 
     mov eax,[prev1]
+    movsx eax,ax
     mov ebx,[filter1]
     imul eax,ebx
     sar eax,8
     add edx,eax
 
     mov eax,[prev0]
+    movsx eax,ax
     mov ebx,[filter0]
     imul eax,ebx
     sar eax,8