diff --git a/Changes b/Changes
index d587b7dbe..6db06004e 100644
--- a/Changes
+++ b/Changes
@@ -3,6 +3,10 @@ Revision history for Verilator
 The contributors that suggested a given feature are shown in [].  [by ...]
 indicates the contributor was also the author of the fix; Thanks!
 
+* Verilator 3.846-devel
+
+****  Fix DETECTARRAY on packed structures, bug610. [Jeremy Bennett]
+
 * Verilator 3.845 2013/02/04
 
 ***   Fix nested packed arrays and struct, bug600. [Jeremy Bennett]
diff --git a/bin/verilator b/bin/verilator
index a71b1cc72..e1e3f72a0 100755
--- a/bin/verilator
+++ b/bin/verilator
@@ -2840,7 +2840,8 @@ correctly.
 =item DETECTARRAY
 
 Error when Verilator tries to deal with a combinatorial loop that could not be
-flattened, and which involves a structure. This typically ocurrs when
+flattened, and which involves a datatype which Verilator cannot handle, such
+as an unpacked struct or a large unpacked array. This typically ocurrs when
 -Wno-UNOPTFLAT has been used to override an UNOPTFLAT warning (see below).
 
 The solution is to break the loop, as described for UNOPTFLAT.
diff --git a/src/V3Changed.cpp b/src/V3Changed.cpp
index 538f00790..4fd034f86 100644
--- a/src/V3Changed.cpp
+++ b/src/V3Changed.cpp
@@ -87,7 +87,9 @@ private:
 	AstVar* varp = vscp->varp();
 	vscp->v3warn(IMPERFECTSCH,"Imperfect scheduling of variable: "<<vscp);
 	AstUnpackArrayDType* arrayp = varp->dtypeSkipRefp()->castUnpackArrayDType();
+	AstStructDType *structp = varp->dtypeSkipRefp()->castStructDType();
 	bool isArray = arrayp;
+	bool isStruct = structp && structp->packed();
 	int msb = isArray ? arrayp->msb() : 0;
 	int lsb = isArray ? arrayp->lsb() : 0;
 	if (isArray && ((msb - lsb + 1) > DETECTARRAY_MAX_INDEXES)) {
@@ -95,7 +97,7 @@ private:
 			 <<" array indexes (probably with UNOPTFLAT warning suppressed): "<<varp->prettyName()<<endl
 			 <<vscp->warnMore()
 			 <<"... Could recompile with DETECTARRAY_MAX_INDEXES increased to at least "<<cvtToStr(msb-lsb+1));
-	} else if (!isArray
+	} else if (!isArray && !isStruct
 		   && !varp->dtypeSkipRefp()->castBasicDType()) {
 	    if (debug()) varp->dumpTree(cout,"-DETECTARRAY-");
 	    vscp->v3warn(E_DETECTARRAY, "Unsupported: Can't detect changes on complex variable (probably with UNOPTFLAT warning suppressed): "<<varp->prettyName());
diff --git a/test_regress/t/t_detectarray_1.pl b/test_regress/t/t_detectarray_1.pl
new file mode 100755
index 000000000..eadb41ee3
--- /dev/null
+++ b/test_regress/t/t_detectarray_1.pl
@@ -0,0 +1,19 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003 by Wilson Snyder. This program is free software; you can
+# redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+
+compile (
+    verilator_flags2 => ["-Wno-UNOPTFLAT"]
+    );
+
+execute (
+    check_finished=>1,
+    );
+
+ok(1);
+1;
diff --git a/test_regress/t/t_detectarray_1.v b/test_regress/t/t_detectarray_1.v
new file mode 100644
index 000000000..73834ea89
--- /dev/null
+++ b/test_regress/t/t_detectarray_1.v
@@ -0,0 +1,41 @@
+// DESCRIPTION: Verilator: Simple test of unoptflat
+//
+// Trigger the DETECTARRAY error.
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2013 by Jeremy Bennett.
+
+localparam ID_MSB = 1;
+
+
+module t (/*AUTOARG*/
+   // Inputs
+   clk
+   );
+   input clk;
+
+   typedef struct packed {
+      logic [ID_MSB:0] 	id;
+   } context_t;
+
+   context_t  tsb;
+
+   assign tsb.id = {tsb.id[0], clk};
+
+   initial begin
+      tsb.id = 0;
+   end
+
+   always @(posedge clk or negedge clk) begin
+
+`ifdef TEST_VERBOSE
+      $write("tsb.id = %x\n", tsb.id);
+`endif
+
+      if (tsb.id[1] != 0) begin
+	 $write("*-* All Finished *-*\n");
+	 $finish;
+      end
+   end
+
+endmodule
diff --git a/test_regress/t/t_detectarray_2.pl b/test_regress/t/t_detectarray_2.pl
new file mode 100755
index 000000000..eadb41ee3
--- /dev/null
+++ b/test_regress/t/t_detectarray_2.pl
@@ -0,0 +1,19 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003 by Wilson Snyder. This program is free software; you can
+# redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+
+compile (
+    verilator_flags2 => ["-Wno-UNOPTFLAT"]
+    );
+
+execute (
+    check_finished=>1,
+    );
+
+ok(1);
+1;
diff --git a/test_regress/t/t_detectarray_2.v b/test_regress/t/t_detectarray_2.v
new file mode 100644
index 000000000..77eb06189
--- /dev/null
+++ b/test_regress/t/t_detectarray_2.v
@@ -0,0 +1,43 @@
+// DESCRIPTION: Verilator: Simple test of unoptflat
+//
+// This should trigger the DETECTARRAY error like t_detectarray_1.v, but in
+// fact it casuses a broken link error. The only difference is that the struct
+// is defined using a constant rather than a localparam.
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2013 by Jeremy Bennett.
+
+localparam ID_MSB = 1;
+
+
+module t (/*AUTOARG*/
+   // Inputs
+   clk
+   );
+   input clk;
+
+   typedef struct packed {
+      logic [1:0] 	id;
+   } context_t;
+
+   context_t  tsb;
+
+   assign tsb.id = {tsb.id[0], clk};
+
+   initial begin
+      tsb.id = 0;
+   end
+
+   always @(posedge clk or negedge clk) begin
+
+`ifdef TEST_VERBOSE
+      $write("tsb.id = %x\n", tsb.id);
+`endif
+
+      if (tsb.id[1] != 0) begin
+	 $write("*-* All Finished *-*\n");
+	 $finish;
+      end
+   end
+
+endmodule