diff --git a/fdtdump.c b/fdtdump.c
index d9fb374..bdc0f94 100644
--- a/fdtdump.c
+++ b/fdtdump.c
@@ -18,7 +18,7 @@
 #include "util.h"
 
 #define FDT_MAGIC_SIZE	4
-#define MAX_VERSION 17
+#define MAX_VERSION 17U
 
 #define ALIGN(x, a)	(((x) + ((a) - 1)) & ~((a) - 1))
 #define PALIGN(p, a)	((void *)(ALIGN((unsigned long)(p), (a))))
@@ -163,7 +163,7 @@ static const char * const usage_opts_help[] = {
 	USAGE_COMMON_OPTS_HELP
 };
 
-static bool valid_header(char *p, off_t len)
+static bool valid_header(char *p, size_t len)
 {
 	if (len < sizeof(struct fdt_header) ||
 	    fdt_magic(p) != FDT_MAGIC ||
@@ -235,7 +235,7 @@ int main(int argc, char *argv[])
 			}
 			++p;
 		}
-		if (!p || endp - p < sizeof(struct fdt_header))
+		if (!p || (size_t)(endp - p) < sizeof(struct fdt_header))
 			die("%s: could not locate fdt magic\n", file);
 		printf("%s: found fdt at offset %#tx\n", file, p - buf);
 		buf = p;