diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index d19eca217c4..5b8151d51ef 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2017-11-30  Pedro Alves  <palves@redhat.com>
+
+	* gdb.linespec/cpls-ops.exp
+	(check_explicit_skips_function_argument): Extract the underlying
+	type of size_t instead of hardcoding it.
+
 2017-11-29  Pedro Alves  <palves@redhat.com>
 
 	PR c++/19436
diff --git a/gdb/testsuite/gdb.linespec/cpls-ops.exp b/gdb/testsuite/gdb.linespec/cpls-ops.exp
index c1b6c33b7b3..d58a6deda20 100644
--- a/gdb/testsuite/gdb.linespec/cpls-ops.exp
+++ b/gdb/testsuite/gdb.linespec/cpls-ops.exp
@@ -43,8 +43,17 @@ proc check_explicit_skips_function_argument {function} {
 # testing operator new.
 
 proc test_operator_new {class_name brackets} {
-    # The type size_t is typedef-ed to.
-    set size_t "unsigned long"
+    global gdb_prompt
+
+    # Extract the type size_t is typedef-ed to.
+    set size_t ""
+    set test "get size_t underlying type"
+    gdb_test_multiple "ptype size_t" $test {
+	-re " = (\[ a-z\]*)\r\n$gdb_prompt $" {
+	    set size_t $expect_out(1,string)
+	    pass "$test"
+	}
+    }
 
     # Complete all prefixes between "operato" and the full prototype.
     foreach cmd_prefix {"b" "b -function"} {