diff --git a/arch/mips/dec/prom/Makefile b/arch/mips/dec/prom/Makefile
index d95016016b42..2bad87551203 100644
--- a/arch/mips/dec/prom/Makefile
+++ b/arch/mips/dec/prom/Makefile
@@ -6,4 +6,4 @@
 
 lib-y			+= init.o memory.o cmdline.o identify.o console.o
 
-lib-$(CONFIG_32BIT)	+= locore.o
+lib-$(CONFIG_CPU_R3000)	+= locore.o
diff --git a/arch/mips/include/asm/dec/prom.h b/arch/mips/include/asm/dec/prom.h
index 62c7dfb90e06..1e1247add1cf 100644
--- a/arch/mips/include/asm/dec/prom.h
+++ b/arch/mips/include/asm/dec/prom.h
@@ -43,16 +43,11 @@
  */
 #define REX_PROM_MAGIC		0x30464354
 
-#ifdef CONFIG_64BIT
-
-#define prom_is_rex(magic)	1	/* KN04 and KN05 are REX PROMs.  */
-
-#else /* !CONFIG_64BIT */
-
-#define prom_is_rex(magic)	((magic) == REX_PROM_MAGIC)
-
-#endif /* !CONFIG_64BIT */
-
+/* KN04 and KN05 are REX PROMs, so only do the check for R3k systems.  */
+static inline bool prom_is_rex(u32 magic)
+{
+	return !IS_ENABLED(CONFIG_CPU_R3000) || magic == REX_PROM_MAGIC;
+}
 
 /*
  * 3MIN/MAXINE PROM entry points for DS5000/1xx's, DS5000/xx's and