diff --git a/arch/x86/math-emu/fpu_emu.h b/arch/x86/math-emu/fpu_emu.h
index afbc4d805d66..c9c320dccca1 100644
--- a/arch/x86/math-emu/fpu_emu.h
+++ b/arch/x86/math-emu/fpu_emu.h
@@ -157,7 +157,7 @@ extern u_char const data_sizes_16[32];
 
 #define signbyte(a) (((u_char *)(a))[9])
 #define getsign(a) (signbyte(a) & 0x80)
-#define setsign(a,b) { if (b) signbyte(a) |= 0x80; else signbyte(a) &= 0x7f; }
+#define setsign(a,b) { if ((b) != 0) signbyte(a) |= 0x80; else signbyte(a) &= 0x7f; }
 #define copysign(a,b) { if (getsign(a)) signbyte(b) |= 0x80; \
                         else signbyte(b) &= 0x7f; }
 #define changesign(a) { signbyte(a) ^= 0x80; }