diff --git a/arch/powerpc/boot/of.h b/arch/powerpc/boot/of.h
index 40d95bf7402b64f10c5ab3f2fdfa63e0db8aa84f..0f058ef69521c00000fed729ef5abb4f202b577a 100644
--- a/arch/powerpc/boot/of.h
+++ b/arch/powerpc/boot/of.h
@@ -23,4 +23,6 @@ typedef u32			__be32;
 #define cpu_to_be32(x) (x)
 #define be32_to_cpu(x) (x)
 
+#define PROM_ERROR (-1u)
+
 #endif /* _PPC_BOOT_OF_H_ */
diff --git a/arch/powerpc/boot/oflib.c b/arch/powerpc/boot/oflib.c
index 0f72b1a42133b8329356f43140e29728851d7bcd..7f61f2eb56535a773a490185d5fe1cbbaab482aa 100644
--- a/arch/powerpc/boot/oflib.c
+++ b/arch/powerpc/boot/oflib.c
@@ -55,7 +55,7 @@ int of_call_prom(const char *service, int nargs, int nret, ...)
 		args.args[nargs+i] = 0;
 
 	if (prom(&args) < 0)
-		return -1;
+		return PROM_ERROR;
 
 	return (nret > 0) ? be32_to_cpu(args.args[nargs]) : 0;
 }
@@ -80,9 +80,9 @@ static int of_call_prom_ret(const char *service, int nargs, int nret,
 		args.args[nargs+i] = 0;
 
 	if (prom(&args) < 0)
-		return -1;
+		return PROM_ERROR;
 
-	if (rets != (void *) 0)
+	if (rets != NULL)
 		for (i = 1; i < nret; ++i)
 			rets[i-1] = be32_to_cpu(args.args[nargs+i]);