diff --git a/src/V3LinkDot.cpp b/src/V3LinkDot.cpp
index 7965a842b..36f6fab19 100644
--- a/src/V3LinkDot.cpp
+++ b/src/V3LinkDot.cpp
@@ -3918,6 +3918,11 @@ class LinkDotResolveVisitor final : public VNVisitor {
                     // Primitive parameter is really a delay2 we can just ignore
                     VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
                     return;
+                } else if (nodep->param() && !nodep->exprp() && !nodep->svDotName()) {
+                    // Placeholder pin the parser makes for an empty '#()', to signal
+                    // the user did type the '#()'. No further use, deleting.
+                    VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
+                    return;
                 } else {
                     const std::string suggest
                         = (nodep->param() ? m_statep->suggestSymFlat(m_pinSymp, nodep->name(),
diff --git a/src/V3Param.cpp b/src/V3Param.cpp
index 1129d730a..c40c9a3a6 100644
--- a/src/V3Param.cpp
+++ b/src/V3Param.cpp
@@ -1886,8 +1886,10 @@ class ParamProcessor final {
         std::vector<AstPin*> pinsByIndex;
         pinsByIndex.resize(m_classTypeParams.size(), nullptr);
         for (AstPin* pinp = paramsp; pinp; pinp = VN_AS(pinp->nextp(), Pin)) {
-            if (AstParamTypeDType* typep = pinp->modPTypep()) {
-                pinsByIndex[m_paramIndex[typep]] = pinp;
+            AstParamTypeDType* const typep = pinp->modPTypep();
+            const auto it = typep ? m_paramIndex.find(typep) : m_paramIndex.end();
+            if (it != m_paramIndex.end()) {
+                pinsByIndex[it->second] = pinp;
             } else {
                 pinsByIndex.push_back(pinp);
             }
diff --git a/test_regress/t/t_class_param_derived_noparam.py b/test_regress/t/t_class_param_derived_noparam.py
new file mode 100755
index 000000000..8a938befd
--- /dev/null
+++ b/test_regress/t/t_class_param_derived_noparam.py
@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# 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-FileCopyrightText: 2026 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.compile()
+
+test.execute()
+
+test.passes()
diff --git a/test_regress/t/t_class_param_derived_noparam.v b/test_regress/t/t_class_param_derived_noparam.v
new file mode 100644
index 000000000..72d678f8c
--- /dev/null
+++ b/test_regress/t/t_class_param_derived_noparam.v
@@ -0,0 +1,105 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain.
+// SPDX-FileCopyrightText: 2026 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=%0x exp=%0x (%s !== %s)\n", `__FILE__,`__LINE__, (gotv), (expv), `"gotv`", `"expv`"); `stop; end while(0);
+// verilog_format: on
+
+// Base class with type parameter
+class base_type #(type T = int);
+  function int width();
+    T t;
+    return $bits(t);
+  endfunction
+endclass
+
+// No type parameters of its own, inherits the base's default
+class default_type extends base_type;
+endclass
+
+// No type parameters of its own, overrides the base's parameter
+class byte_type extends base_type #(byte);
+endclass
+
+// No type parameters of its own, empty parameter list on the extends clause
+class paren_type extends base_type#();
+endclass
+
+// Base class with value parameter
+class base_val #(int N = 32);
+  function int val();
+    return N;
+  endfunction
+endclass
+
+// No parameters of its own, inherits the base's default
+class default_val extends base_val;
+endclass
+
+// No parameters of its own, overrides the base's parameter
+class eight_val extends base_val #(8);
+endclass
+
+// No parameters of its own, empty parameter list on the extends clause
+class paren_val extends base_val#();
+endclass
+
+// Base class with no parameters at all
+class base_none;
+  function int width();
+    return 1;
+  endfunction
+endclass
+
+class paren_none extends base_none#();
+endclass
+
+class noparen_none extends base_none;
+endclass
+
+module t;
+
+  // Referenced with an empty parameter list, and without one
+  default_type#() dp = new;
+  default_type dn = new;
+  byte_type#() bp = new;
+  byte_type bn = new;
+  paren_type#() tp = new;
+  paren_type tn = new;
+  default_val#() vp = new;
+  default_val vn = new;
+  eight_val#() ep = new;
+  eight_val en = new;
+  paren_val#() qp = new;
+  paren_val qn = new;
+  paren_none#() pp = new;
+  paren_none pn = new;
+  noparen_none#() np = new;
+  noparen_none nn = new;
+
+  initial begin
+    `checkh(dp.width(), 32);
+    `checkh(dn.width(), 32);
+    `checkh(bp.width(), 8);
+    `checkh(bn.width(), 8);
+    `checkh(tp.width(), 32);
+    `checkh(tn.width(), 32);
+    `checkh(vp.val(), 32);
+    `checkh(vn.val(), 32);
+    `checkh(ep.val(), 8);
+    `checkh(en.val(), 8);
+    `checkh(qp.val(), 32);
+    `checkh(qn.val(), 32);
+    `checkh(pp.width(), 1);
+    `checkh(pn.width(), 1);
+    `checkh(np.width(), 1);
+    `checkh(nn.width(), 1);
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+
+endmodule