diff --git a/src/core/p-checksum.c b/src/core/p-checksum.c
index febccd3cf1..28a3f4754d 100644
--- a/src/core/p-checksum.c
+++ b/src/core/p-checksum.c
@@ -240,6 +240,7 @@
 		}
 		args = Find_Refines(ds, ALL_WRITE_REFS);
 		arg = D_ARG(2);
+		if (!ANY_BINSTR(arg)) Trap_Arg(arg);
 		REBI64  pos = (REBI64)VAL_INDEX(arg);
 		if (args & AM_WRITE_SEEK) {
 			pos += Int64(D_ARG(ARG_WRITE_INDEX));
diff --git a/src/tests/units/checksum-test.r3 b/src/tests/units/checksum-test.r3
index 0ffc8bdb0f..953bf34fca 100644
--- a/src/tests/units/checksum-test.r3
+++ b/src/tests/units/checksum-test.r3
@@ -208,6 +208,10 @@ if find system/catalog/checksums 'ripemd160 [
 		;opening already opened port restarts computation
 		--assert sum1 = read write/seek/part open port #{cafe0bad} 2 2
 		--assert sum1 = read write/seek/part open port tail #{cafe0bad} -2 2
+
+	--test-- "checksum port with invalid argument"
+	;@@ https://github.com/Oldes/Rebol-issues/issues/2553
+		--assert all [error? e: try [write checksum:md5 1]  e/id = 'invalid-arg]
 ===end-group===
 
 ===start-group=== "Checksum HMAC SHA"