diff --git a/gcc/fortran/data.c b/gcc/fortran/data.c
index 25e97930169..71e2552025d 100644
--- a/gcc/fortran/data.c
+++ b/gcc/fortran/data.c
@@ -595,6 +595,9 @@ gfc_assign_data_value (gfc_expr *lvalue, gfc_expr *rvalue, mpz_t index,
       /* An initializer has to be constant.  */
       if (lvalue->ts.u.cl->length == NULL && !(ref && ref->u.ss.length != NULL))
 	return false;
+      if (lvalue->ts.u.cl->length
+	  && lvalue->ts.u.cl->length->expr_type != EXPR_CONSTANT)
+	return false;
       expr = create_character_initializer (init, last_ts, ref, rvalue);
       if (!expr)
 	return false;
diff --git a/gcc/testsuite/gfortran.dg/pr99205.f90 b/gcc/testsuite/gfortran.dg/pr99205.f90
new file mode 100644
index 00000000000..ed0782ce8a0
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr99205.f90
@@ -0,0 +1,11 @@
+! { dg-do compile }
+! PR fortran/99205 - Out of memory with undefined character length
+! { dg-options "-w" }
+
+program p
+  character(l) :: c(2) ! { dg-error "must have constant character length" }
+  data c /'a', 'b'/
+  common c
+end
+
+! { dg-error "cannot appear in the expression at" " " { target *-*-* } 6 }