diff --git a/src/V3AstNodeDType.h b/src/V3AstNodeDType.h
index 4cb67cfa2..5ccec4121 100644
--- a/src/V3AstNodeDType.h
+++ b/src/V3AstNodeDType.h
@@ -1171,11 +1171,13 @@ class AstRefDType final : public AstNodeDType {
     //
     // Pre-Width must reference the Typeref, not what it points to, as some child
     // types like AstBracketArrayType will disappear and can't lose the handle
+    //
     // @astgen ptr := m_typedefp : Optional[AstTypedef]  // Referenced type
     // Post-width typedefs are removed and point to type directly
     // @astgen ptr := m_refDTypep : Optional[AstNodeDType]  // Data type references
     // @astgen ptr := m_classOrPackagep : Optional[AstNodeModule]  // Class/package defined in
     string m_name;  // Name of an AstTypedef
+    string m_ifacePortName;  // Name of pre-dot interface port identifier
 public:
     AstRefDType(FileLine* fl, const string& name)
         : ASTGEN_SUPER_RefDType(fl)
@@ -1192,6 +1194,11 @@ public:
         this->typeofp(typeofp);
         if (AstNodeDType* const dtp = VN_CAST(typeofp, NodeDType)) refDTypep(dtp);
     }
+    class FlagIfaceTypedef {};
+    AstRefDType(FileLine* fl, FlagIfaceTypedef, const string& ifc, const string& name)
+        : ASTGEN_SUPER_RefDType(fl)
+        , m_name{name}
+        , m_ifacePortName{ifc} {}
     ASTGEN_MEMBERS_AstRefDType;
     // METHODS
     bool sameNode(const AstNode* samep) const override {
@@ -1206,6 +1213,7 @@ public:
     void dumpJson(std::ostream& str = std::cout) const override;
     void dumpSmall(std::ostream& str) const override;
     string name() const override VL_MT_STABLE { return m_name; }
+    string ifacePortName() const { return m_ifacePortName; }
     string prettyDTypeName(bool full) const override {
         return subDTypep() ? prettyName(subDTypep()->prettyDTypeName(full)) : prettyName();
     }
diff --git a/src/V3AstNodes.cpp b/src/V3AstNodes.cpp
index 195fc31b7..e66684ccd 100644
--- a/src/V3AstNodes.cpp
+++ b/src/V3AstNodes.cpp
@@ -2318,10 +2318,15 @@ void AstRefDType::dump(std::ostream& str) const {
             s_recursing = false;
         }
     } else {
+        if (!ifacePortName().empty()) str << " ifcPort=" << ifacePortName();
         str << " -> UNLINKED";
     }
 }
-void AstRefDType::dumpJson(std::ostream& str) const { dumpJsonGen(str); }
+void AstRefDType::dumpJson(std::ostream& str) const {
+    if (!ifacePortName().empty()) dumpJsonStr(str, "ifcPortName", ifacePortName());
+    dumpJsonGen(str);
+}
+
 void AstRefDType::dumpSmall(std::ostream& str) const {
     this->AstNodeDType::dumpSmall(str);
     str << "ref";
diff --git a/src/V3LinkDot.cpp b/src/V3LinkDot.cpp
index 8a38c03a0..255080a32 100644
--- a/src/V3LinkDot.cpp
+++ b/src/V3LinkDot.cpp
@@ -4961,6 +4961,9 @@ class LinkDotResolveVisitor final : public VNVisitor {
             const VSymEnt* foundp;
             if (nodep->classOrPackagep()) {
                 foundp = m_statep->getNodeSym(nodep->classOrPackagep())->findIdFlat(nodep->name());
+            } else if (!nodep->ifacePortName().empty()) {  // Interface typedef
+                nodep->v3error("Unsupported: SystemVerilog 2005 interface typedef");
+                return;
             } else if (m_ds.m_dotPos == DP_FIRST || m_ds.m_dotPos == DP_NONE) {
                 foundp = m_curSymp->findIdFallback(nodep->name());
             } else {
diff --git a/src/verilog.y b/src/verilog.y
index 64e57038d..19b81dfed 100644
--- a/src/verilog.y
+++ b/src/verilog.y
@@ -2516,8 +2516,9 @@ type_declaration<nodep>:        // ==IEEE: type_declaration
                           AstNodeDType* const dtp = GRAMMARP->createArray(refp, $4, true);
                           $$ = GRAMMARP->createTypedef($<fl>5, *$5, $7, dtp, $6); }
         //                      //
-        |       yTYPEDEF idAny/*interface*/ '.' idAny/*type*/ idAny/*type*/ dtypeAttrListE ';'
-                        { $$ = nullptr; BBUNSUP($1, "Unsupported: SystemVerilog 2005 typedef in this context"); DEL($6); }
+        |       yTYPEDEF idAny/*interface_port*/ '.' idAny/*type*/ idAny/*type*/ dtypeAttrListE ';'
+                        { AstRefDType* const refp = new AstRefDType{$<fl>2, AstRefDType::FlagIfaceTypedef{}, *$2, *$4};
+                          $$ = GRAMMARP->createTypedef($<fl>5, *$5, $6, refp, nullptr); }
         //                      // idAny as also allows redeclaring same typedef again
         |       yTYPEDEF idAny ';'                      { $$ = GRAMMARP->createTypedefFwd($<fl>2, *$2, VFwdType::NONE); }
         //                      // IEEE: expanded forward_type to prevent conflict
diff --git a/test_regress/t/t_interface_typedef.out b/test_regress/t/t_interface_typedef.out
index ab677162e..fe9d6e06f 100644
--- a/test_regress/t/t_interface_typedef.out
+++ b/test_regress/t/t_interface_typedef.out
@@ -1,5 +1,5 @@
-%Error-UNSUPPORTED: t/t_interface_typedef.v:46:4: Unsupported: SystemVerilog 2005 typedef in this context
-   46 |    typedef ifc_if.struct_t struct_t;
-      |    ^~~~~~~
-                    ... For error description see https://verilator.org/warn/UNSUPPORTED?v=latest
+%Error: t/t_interface_typedef.v:49:11: Unsupported: SystemVerilog 2005 interface typedef
+   49 |   typedef ifc_if.struct_t struct_t;
+      |           ^~~~~~
+        ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
 %Error: Exiting due to
diff --git a/test_regress/t/t_interface_typedef.py b/test_regress/t/t_interface_typedef.py
index 966dc53da..da7d64435 100755
--- a/test_regress/t/t_interface_typedef.py
+++ b/test_regress/t/t_interface_typedef.py
@@ -9,9 +9,11 @@
 
 import vltest_bootstrap
 
-test.scenarios('simulator')
+test.scenarios('simulator_st')
 
-test.compile(fails=test.vlt_all, expect_filename=test.golden_filename)
+test.compile(verilator_flags2=['--binary'],
+             fails=test.vlt_all,
+             expect_filename=test.golden_filename)
 
 if not test.vlt_all:
     test.execute()
diff --git a/test_regress/t/t_interface_typedef.v b/test_regress/t/t_interface_typedef.v
index c3491894d..2085e38bc 100644
--- a/test_regress/t/t_interface_typedef.v
+++ b/test_regress/t/t_interface_typedef.v
@@ -4,54 +4,58 @@
 // any use, without warranty, 2021 by Wilson Snyder.
 // SPDX-License-Identifier: CC0-1.0
 
+// verilog_format: off
 `define stop $stop
-`define checkh(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got='h%x exp='h%x\n", `__FILE__,`__LINE__, (gotv), (expv)); `stop; end while(0)
+`define checkh(gotv, expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got='h%x exp='h%x\n", `__FILE__,`__LINE__, (gotv), (expv)); `stop; end while(0)
+// verilog_format: on
 
-interface ifc
-  #(
+interface ifc #(
     parameter int unsigned WIDTH
-    ) ();
-   typedef struct {
-     logic [WIDTH-1:0] data;
-   } struct_t;
+) ();
+  typedef struct {logic [WIDTH-1:0] data;} struct_t;
 endinterface
 
-module t (/*AUTOARG*/
-   // Inputs
-   clk
-   );
-   input clk;
+module t (  /*AUTOARG*/
+    // Inputs
+    clk
+);
+  input clk;
 
-   ifc #(10) i_ifc10();
-   ifc #(20) i_ifc20();
+  ifc #(10) i_ifc10 ();
+  ifc #(20) i_ifc20 ();
 
-   sub #(10) u_sub10 (.clk, .ifc_if(i_ifc10));
-   sub #(20) u_sub20 (.clk, .ifc_if(i_ifc20));
+  sub #(10) u_sub10 (
+      .clk,
+      .ifc_if(i_ifc10)
+  );
+  sub #(20) u_sub20 (
+      .clk,
+      .ifc_if(i_ifc20)
+  );
 
-   integer cyc = 1;
-   always @ (posedge clk) begin
-      cyc <= cyc + 1;
-      if (cyc==20) begin
-         $write("*-* All Finished *-*\n");
-         $finish;
-      end
-   end
+  initial begin
+    #100;
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
 endmodule
 
 module sub #(
-     parameter int EXP_WIDTH)
-   (
+    parameter int EXP_WIDTH
+) (
     input logic clk,
-    ifc ifc_if);
-   typedef ifc_if.struct_t struct_t;
+    ifc ifc_if
+);
+  typedef ifc_if.struct_t struct_t;
 
-   wire [EXP_WIDTH-1:0] expval = '1;
+  wire [EXP_WIDTH-1:0] expval = '1;
 
-   initial begin
-      struct_t substruct;
-      substruct.data = '1;
-      `checkh($bits(struct_t), EXP_WIDTH);
-      `checkh(substruct.data, expval);
-   end
+  initial begin
+    struct_t substruct;
+    #10;
+    substruct.data = '1;
+    `checkh($bits(struct_t), EXP_WIDTH);
+    `checkh(substruct.data, expval);
+  end
 
 endmodule
diff --git a/test_regress/t/t_interface_typedef2.out b/test_regress/t/t_interface_typedef2.out
new file mode 100644
index 000000000..7f8fee0bd
--- /dev/null
+++ b/test_regress/t/t_interface_typedef2.out
@@ -0,0 +1,11 @@
+%Error: t/t_interface_typedef2.v:37:11: Unsupported: SystemVerilog 2005 interface typedef
+   37 |   typedef p1.stage_t stage1_t;   
+      |           ^~
+        ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
+%Error: t/t_interface_typedef2.v:40:11: Unsupported: SystemVerilog 2005 interface typedef
+   40 |   typedef p2.stage_t stage2_t;   
+      |           ^~
+%Error: t/t_interface_typedef2.v:25:11: Unsupported: SystemVerilog 2005 interface typedef
+   25 |   typedef p1.stage_t stage_t;   
+      |           ^~
+%Error: Exiting due to
diff --git a/test_regress/t/t_interface_typedef2.py b/test_regress/t/t_interface_typedef2.py
new file mode 100755
index 000000000..da7d64435
--- /dev/null
+++ b/test_regress/t/t_interface_typedef2.py
@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 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.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator_st')
+
+test.compile(verilator_flags2=['--binary'],
+             fails=test.vlt_all,
+             expect_filename=test.golden_filename)
+
+if not test.vlt_all:
+    test.execute()
+
+test.passes()
diff --git a/test_regress/t/t_interface_typedef2.v b/test_regress/t/t_interface_typedef2.v
new file mode 100644
index 000000000..b54aa9dbc
--- /dev/null
+++ b/test_regress/t/t_interface_typedef2.v
@@ -0,0 +1,65 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2025 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+interface common_intf #(
+    int ADDR_W,
+    DATA_W
+);
+  typedef struct packed {
+
+    logic [ADDR_W-1:0] cntr_idx;
+    logic [DATA_W-1:0] cntr_val;
+
+  } stage_t;
+
+  stage_t bus;
+
+endinterface
+
+module mod1 (
+    common_intf p1
+);
+  typedef p1.stage_t stage_t;  // "imports" type into module
+  stage_t local_bus;
+
+  initial begin
+    $display("%m mod1: idx bits %0d, val bits %0d", $bits(p1.bus.cntr_idx), $bits(p1.bus.cntr_val));
+  end
+endmodule
+
+module mod2 (
+    common_intf p1,
+    p2
+);
+  typedef p1.stage_t stage1_t;  // "imports" type into module
+  stage1_t local_bus1;
+
+  typedef p2.stage_t stage2_t;  // "imports" type into module
+  stage2_t local_bus2;
+
+  initial begin
+    $display("%m-1 mod2: idx bits %0d, val bits %0d", $bits(p1.bus.cntr_idx), $bits(p1.bus.cntr_val));
+    $display("%m-2 mod2: idx bits %0d, val bits %0d", $bits(p2.bus.cntr_idx), $bits(p2.bus.cntr_val));
+    $display("%m mod2: params p1 ADDR_W %0d DATA_W %0d", p1.ADDR_W, p1.DATA_W);
+    $display("%m mod2: params p2 ADDR_W %0d DATA_W %0d", p2.ADDR_W, p2.DATA_W);
+  end
+
+endmodule
+
+module t;
+  common_intf #(8, 16) i1_2 ();  // connects m1 to m2
+  common_intf #(4, 32) i2_3 ();  // connects m2 to m3
+  mod1 m1 (i1_2);
+  mod2 m2 (
+      i1_2,
+      i2_3
+  );
+  mod1 m3 (i2_3);
+  initial begin
+    #10;
+    $finish;
+  end
+endmodule
diff --git a/test_regress/t/t_interface_typedef3.out b/test_regress/t/t_interface_typedef3.out
new file mode 100644
index 000000000..81f7b6d6c
--- /dev/null
+++ b/test_regress/t/t_interface_typedef3.out
@@ -0,0 +1,5 @@
+%Error: t/t_interface_typedef3.v:22:11: Unsupported: SystemVerilog 2005 interface typedef
+   22 |   typedef iface_mp.choice_t tdef_t;
+      |           ^~~~~~~~
+        ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
+%Error: Exiting due to
diff --git a/test_regress/t/t_interface_typedef3.py b/test_regress/t/t_interface_typedef3.py
new file mode 100755
index 000000000..da7d64435
--- /dev/null
+++ b/test_regress/t/t_interface_typedef3.py
@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 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.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator_st')
+
+test.compile(verilator_flags2=['--binary'],
+             fails=test.vlt_all,
+             expect_filename=test.golden_filename)
+
+if not test.vlt_all:
+    test.execute()
+
+test.passes()
diff --git a/test_regress/t/t_interface_typedef3.v b/test_regress/t/t_interface_typedef3.v
new file mode 100644
index 000000000..f77507742
--- /dev/null
+++ b/test_regress/t/t_interface_typedef3.v
@@ -0,0 +1,32 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2025 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+// verilog_format: off
+`define stop $stop
+`define checkd(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got=%0d exp=%0d (%s !== %s)\n", `__FILE__,`__LINE__, (gotv), (expv), `"gotv`", `"expv`"); `stop; end while(0);
+// verilog_format: on
+
+interface ifc;
+  typedef logic [3:0] choice_t;
+  choice_t q;
+  localparam int ONE = 1;
+  modport mp(input q);
+endinterface
+
+module sub (
+    interface.mp iface_mp
+);
+  typedef iface_mp.choice_t tdef_t;
+  tdef_t P;
+  initial begin
+    `checkd($bits(tdef_t), 4);
+  end
+endmodule
+
+module t;
+  ifc u_ifc ();
+  sub u_sub (u_ifc.mp);
+endmodule
diff --git a/test_regress/t/t_interface_typedef_bad.out b/test_regress/t/t_interface_typedef_bad.out
new file mode 100644
index 000000000..1c91f464c
--- /dev/null
+++ b/test_regress/t/t_interface_typedef_bad.out
@@ -0,0 +1,11 @@
+%Error: t/t_interface_typedef_bad.v:15:11: Unsupported: SystemVerilog 2005 interface typedef
+   15 |   typedef not_found.choice_t choice1_t;   
+      |           ^~~~~~~~~
+        ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
+%Error: t/t_interface_typedef_bad.v:16:11: Unsupported: SystemVerilog 2005 interface typedef
+   16 |   typedef i.not_found_t choice2_t;   
+      |           ^
+%Error: t/t_interface_typedef_bad.v:17:11: Unsupported: SystemVerilog 2005 interface typedef
+   17 |   typedef not_ifc.x_t choice3_t;   
+      |           ^~~~~~~
+%Error: Exiting due to
diff --git a/test_regress/t/t_interface_typedef_bad.py b/test_regress/t/t_interface_typedef_bad.py
new file mode 100755
index 000000000..30c3d4f77
--- /dev/null
+++ b/test_regress/t/t_interface_typedef_bad.py
@@ -0,0 +1,16 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 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.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('linter')
+
+test.lint(fails=test.vlt_all, expect_filename=test.golden_filename)
+
+test.passes()
diff --git a/test_regress/t/t_interface_typedef_bad.v b/test_regress/t/t_interface_typedef_bad.v
new file mode 100644
index 000000000..e71a0bcc3
--- /dev/null
+++ b/test_regress/t/t_interface_typedef_bad.v
@@ -0,0 +1,23 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2025 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+interface ifc;
+  integer i;
+endinterface
+
+module sub (
+    interface i
+);
+  logic not_ifc;
+  typedef not_found.choice_t choice1_t;  // <--- Error: not found interface port
+  typedef i.not_found_t choice2_t;  // <--- Error: not found typedef
+  typedef not_ifc.x_t choice3_t;  // <--- Error: sub not interface reference
+endmodule
+
+module t;
+  ifc u_ifc ();
+  sub u_sub (u_ifc);
+endmodule