diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 739f0e145e17..f34ea88fb995 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,8 @@
 2006-05-15  Volker Reichelt  <reichelt@igpm.rwth-aachen.de>
 
+	PR c++/27315
+	* pt.c (do_decl_instantiation): Return early on invalid decl.
+
 	PR c++/27559
 	* pt.c (push_template_decl_real): Return error_mark_node instead
 	of broken decl.
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index bcf209657648..cf0e7cd4f9a0 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -11215,7 +11215,7 @@ do_decl_instantiation (tree decl, tree storage)
   tree result = NULL_TREE;
   int extern_p = 0;
 
-  if (!decl)
+  if (!decl || decl == error_mark_node)
     /* An error occurred, for which grokdeclarator has already issued
        an appropriate message.  */
     return;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c7ef3aeae72e..df0864627f3f 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,9 @@
 2006-05-15  Volker Reichelt  <reichelt@igpm.rwth-aachen.de>
 
+	PR c++/27315
+	* g++.dg/template/operator6.C: New test.
+	* g++.dg/template/incomplete3.C: New test.
+
 	PR c++/27559
 	* g++.dg/template/new4.C: New test.
 
diff --git a/gcc/testsuite/g++.dg/template/incomplete3.C b/gcc/testsuite/g++.dg/template/incomplete3.C
new file mode 100644
index 000000000000..8a20bba74d57
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/incomplete3.C
@@ -0,0 +1,5 @@
+// PR c++/27315
+// { dg-do compile }
+
+struct A;                  // { dg-error "forward declaration" }
+template void A::foo<0>(); // { dg-error "before|incomplete" }
diff --git a/gcc/testsuite/g++.dg/template/operator6.C b/gcc/testsuite/g++.dg/template/operator6.C
new file mode 100644
index 000000000000..94a869bccd5f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/operator6.C
@@ -0,0 +1,4 @@
+// PR c++/27315
+// { dg-do compile }
+
+template void operator+; // { dg-error "non-function" }