diff --git a/arch/m32r/kernel/smp.c b/arch/m32r/kernel/smp.c
index 8a88f1f..31cef20 100644
--- a/arch/m32r/kernel/smp.c
+++ b/arch/m32r/kernel/smp.c
@@ -806,7 +806,7 @@
 
 	if (mask & ~physids_coerce(phys_cpu_present_map))
 		BUG();
-	if (ipi_num >= NR_IPIS)
+	if (ipi_num >= NR_IPIS || ipi_num < 0)
 		BUG();
 
 	mask <<= IPI_SHIFT;