diff --git a/gas/testsuite/gas/all/diff1.s b/gas/testsuite/gas/all/diff1.s
new file mode 100644
index 00000000000..10a89fdc4e5
--- /dev/null
+++ b/gas/testsuite/gas/all/diff1.s
@@ -0,0 +1,5 @@
+# Difference of two undefined symbols.
+# The assembler should reject this.
+	.text
+	.globl _foo
+_foo:	.long _a - _b