diff --git a/src/dehumanize_number.c b/src/dehumanize_number.c
index 640f1fb..632bf1d 100644
--- a/src/dehumanize_number.c
+++ b/src/dehumanize_number.c
@@ -1,5 +1,5 @@
 /*
- * Copyright © 2012 Guillem Jover <guillem@hadrons.org>
+ * Copyright © 2012-2013 Guillem Jover <guillem@hadrons.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -35,8 +35,8 @@
 int
 dehumanize_number(const char *buf, int64_t *num)
 {
-	uint64_t rval;
-	int sign = 1;
+	uint64_t rval, rmax;
+	int sign = +1;
 	int rc;
 
 	/* The current expand_number() implementation uses bit shifts, so
@@ -52,7 +52,13 @@ dehumanize_number(const char *buf, int64_t *num)
 	rc = expand_number(buf, &rval);
 	if (rc < 0)
 		return rc;
-	if (rval == UINT64_MAX && sign == -1) {
+
+	/* The sign has been stripped, so rval has the absolute value.
+	 * Error out, regardless of the sign, if rval is greater than
+	 * abs(INT64_MIN) (== INT64_MAX + 1), or if the sign is positive
+	 * and the value has overflown by one (INT64_MAX + 1). */
+	rmax = INT64_MAX + 1ULL;
+	if (rval > rmax || (rval == rmax && sign == +1)) {
 		errno = ERANGE;
 		return -1;
 	}
diff --git a/test/humanize.c b/test/humanize.c
index 0e8f0cf..59e4cde 100644
--- a/test/humanize.c
+++ b/test/humanize.c
@@ -25,6 +25,7 @@
  */
 
 #include <assert.h>
+#include <errno.h>
 #include <stdlib.h>
 
 int
@@ -60,5 +61,17 @@ main(int argc, char **argv)
 	assert(dehumanize_number("-3G", &val) == 0);
 	assert(val == -3221225472LL);
 
+	assert(dehumanize_number("9223372036854775807", &val) == 0);
+	assert(val == INT64_MAX);
+
+	assert(dehumanize_number("9223372036854775808", &val) == -1);
+	assert(errno == ERANGE);
+
+	assert(dehumanize_number("-9223372036854775808", &val) == 0);
+	assert(val == INT64_MIN);
+
+	assert(dehumanize_number("-9223372036854775809", &val) == -1);
+	assert(errno == ERANGE);
+
 	return 0;
 }