diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index d0122c7b024..ee7eab080cb 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2019-05-29  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/89875
+	* parser.c (cp_parser_sizeof_operand): When the type-id production
+	did not work out commit to the tentative parse.
+
 2019-05-29  Jakub Jelinek  <jakub@redhat.com>
 
 	P1091R3 - Extending structured bindings to be more like var decls
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 08b4105c97f..1de35da83ec 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -28942,6 +28942,8 @@ cp_parser_sizeof_operand (cp_parser* parser, enum rid keyword)
     {
       tree type = NULL_TREE;
 
+      tentative_firewall firewall (parser);
+
       /* We can't be sure yet whether we're looking at a type-id or an
 	 expression.  */
       cp_parser_parse_tentatively (parser);
@@ -28969,11 +28971,15 @@ cp_parser_sizeof_operand (cp_parser* parser, enum rid keyword)
       /* If all went well, then we're done.  */
       if (cp_parser_parse_definitely (parser))
 	expr = type;
-    }
+      else
+	{
+	  /* Commit to the tentative_firewall so we get syntax errors.  */
+	  cp_parser_commit_to_tentative_parse (parser);
 
-  /* If the type-id production did not work out, then we must be
-     looking at the unary-expression production.  */
-  if (!expr)
+	  expr = cp_parser_unary_expression (parser);
+	}
+    }
+  else
     expr = cp_parser_unary_expression (parser);
 
   /* Go back to evaluating expressions.  */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a2d46357e39..19971c9a1ba 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,7 +1,13 @@
+2019-05-29  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/89875
+	* g++.dg/cpp0x/decltype-pr66548.C: Remove xfail.
+	* g++.dg/template/sizeof-template-argument.C: Adjust expected error.
+
 2019-05-29  Alejandro Martinez  <alejandro.martinezvicente@arm.com>
 
-	* gcc.target/aarch64/sve2/aarch64-sve2.exp: New file, regression driver
-	for AArch64 SVE2.
+	* gcc.target/aarch64/sve2/aarch64-sve2.exp: New file, regression
+	driver for AArch64 SVE2.
 	* gcc.target/aarch64/sve2/average_1.c: New test.
 	* lib/target-supports.exp (check_effective_target_aarch64_sve2): New
 	helper.
diff --git a/gcc/testsuite/g++.dg/cpp0x/decltype-pr66548.C b/gcc/testsuite/g++.dg/cpp0x/decltype-pr66548.C
index 93a7d490f2f..3757b671fdd 100644
--- a/gcc/testsuite/g++.dg/cpp0x/decltype-pr66548.C
+++ b/gcc/testsuite/g++.dg/cpp0x/decltype-pr66548.C
@@ -11,7 +11,7 @@ struct Meow {};
 
 void f ()
 {
-  decltype (Meow.purr ()) d;   // { dg-error "expected primary-expression" "pr89875" { xfail c++98_only } }
+  decltype (Meow.purr ()) d;   // { dg-error "expected primary-expression" }
   (void)&d;
 }
 
diff --git a/gcc/testsuite/g++.dg/template/sizeof-template-argument.C b/gcc/testsuite/g++.dg/template/sizeof-template-argument.C
index 31aeeec9bfc..2bfff6d9a18 100644
--- a/gcc/testsuite/g++.dg/template/sizeof-template-argument.C
+++ b/gcc/testsuite/g++.dg/template/sizeof-template-argument.C
@@ -3,9 +3,9 @@
 
 template<int> struct A {};
 
-template<typename> struct B : A <sizeof(=)> {}; /* { dg-error "template argument" } */
+template<typename> struct B : A <sizeof(=)> {}; /* { dg-error "expected primary-expression" } */
 
-template<typename> struct C : A <sizeof(=)> {}; /* { dg-error "template argument" } */
+template<typename> struct C : A <sizeof(=)> {}; /* { dg-error "expected primary-expression" } */
 
 int a;