diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index ab2665098791..8b9f90eeb0ff 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,9 @@
+2017-10-18  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/79795
+	* resolve.c (resovle_symbol): Change gcc_assert to
+	sensible error message.
+
 2017-10-18  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/82550
diff --git a/gcc/fortran/resolve.c b/gcc/fortran/resolve.c
index 5e4988e69451..178854bb0ae8 100644
--- a/gcc/fortran/resolve.c
+++ b/gcc/fortran/resolve.c
@@ -14403,7 +14403,23 @@ resolve_symbol (gfc_symbol *sym)
 
   if (as)
     {
-      gcc_assert (as->type != AS_IMPLIED_SHAPE);
+      /* If AS_IMPLIED_SHAPE makes it to here, it must be a bad
+	 specification expression.  */
+      if (as->type == AS_IMPLIED_SHAPE)
+	{
+	  int i;
+	  for (i=0; i<as->rank; i++)
+	    {
+	      if (as->lower[i] != NULL && as->upper[i] == NULL)
+		{
+		  gfc_error ("Bad specification for assumed size array at %L",
+			     &as->lower[i]->where);
+		  return;
+		}
+	    }
+	  gcc_unreachable();
+	}
+
       if (((as->type == AS_ASSUMED_SIZE && !as->cp_was_assumed)
 	   || as->type == AS_ASSUMED_SHAPE)
 	  && !sym->attr.dummy && !sym->attr.select_type_temporary)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c44b420782f1..a792c359d006 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-10-18  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/79795
+	* gfortran.dg/assumed_size_2.f90: New test.
+
 2017-10-18  Uros Bizjak  <ubizjak@gmail.com>
 	    Jakub Jelinek  <jakub@redhat.com>
 
diff --git a/gcc/testsuite/gfortran.dg/assumed_size_2.f90 b/gcc/testsuite/gfortran.dg/assumed_size_2.f90
new file mode 100644
index 000000000000..e9a1185b5273
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/assumed_size_2.f90
@@ -0,0 +1,4 @@
+! { dg-do compile }
+subroutine foo(a)
+  dimension  a(*,*) ! { dg-error "Bad specification for assumed size array" }
+end