diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 482f4a5d543ec982664daf63defc14c5364da251..c5470be129a08c96fc969595ecfb29a2280958ac 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2006-05-30  Volker Reichelt  <reichelt@igpm.rwth-aachen.de>
+
+	PR c/27718
+	* c-typeck.c (c_expr_sizeof_type): Handle invalid types.
+
 2006-05-30  Zdenek Dvorak <dvorakz@suse.cz>
 
 	PR tree-optimization/27779
diff --git a/gcc/c-typeck.c b/gcc/c-typeck.c
index 7a8cdc40e2398101928150a69195ab40bc3384e1..2c5736cf769e505075c1a2aba51675e5463126b4 100644
--- a/gcc/c-typeck.c
+++ b/gcc/c-typeck.c
@@ -2153,7 +2153,8 @@ c_expr_sizeof_type (struct c_type_name *t)
   type = groktypename (t);
   ret.value = c_sizeof (type);
   ret.original_code = ERROR_MARK;
-  pop_maybe_used (C_TYPE_VARIABLE_SIZE (type));
+  pop_maybe_used (type != error_mark_node
+		  ? C_TYPE_VARIABLE_SIZE (type) : false);
   return ret;
 }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index eedd466c2ca00d79566759d8665eb2eb0e0e1ddc..dc0ec7cf69894f96c2ffb2fa71bcd5ed44e120b9 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2006-05-30  Volker Reichelt  <reichelt@igpm.rwth-aachen.de>
+
+	PR c/27718
+	* gcc.dg/sizeof-1.c: New test.
+
 2006-05-30  Uros Bizjak  <uros@kss-loka.si>
 
 	PR target/27790
diff --git a/gcc/testsuite/gcc.dg/sizeof-1.c b/gcc/testsuite/gcc.dg/sizeof-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..9541a4c273ad5de0b701d1aa01dd95efa06bb5ca
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/sizeof-1.c
@@ -0,0 +1,4 @@
+/* PR c/27718 */
+/* { dg-do compile } */
+
+int i = sizeof(struct A[]);  /* { dg-error "incomplete" } */