1 files changed, 6 insertions, 1 deletions
diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index e4b0f61f8..92b46c296 100644
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -648,7 +648,12 @@ nicenumtoull(const char *buf)
 	} else if (end[0] == '.') {
 		double fval = strtod(buf, &end);
 		fval *= pow(2, str2shift(end));
-		if (fval > UINT64_MAX) {
+		/*
+		 * UINT64_MAX is not exactly representable as a double.
+		 * The closest representation is UINT64_MAX + 1, so we
+		 * use a >= comparison instead of > for the bounds check.
+		 */
+		if (fval >= (double)UINT64_MAX) {
 			(void) fprintf(stderr, "ztest: value too large: %s\n",
 			    buf);
 			usage(B_FALSE);