diff --git a/configure.ac b/configure.ac
index 1aa353ed7..9315730f4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -474,6 +474,7 @@ AC_SUBST(CFG_LDFLAGS_VERILATED)
 # pthreads is harmless otherwise.
 CFG_LIBS="$LIBS $CFG_LIBS"
 _MY_LDLIBS_CHECK_OPT(CFG_LIBS, -lpthread)
+_MY_LDLIBS_CHECK_OPT(CFG_LIBS, -latomic)
 
 # Check libraries for MingW
 _MY_LDLIBS_CHECK_OPT(CFG_LIBS, -lbcrypt)
diff --git a/src/V3EmitCFunc.h b/src/V3EmitCFunc.h
index b68dc0c83..aedd96a91 100644
--- a/src/V3EmitCFunc.h
+++ b/src/V3EmitCFunc.h
@@ -248,16 +248,18 @@ public:
         return nullptr;
     }
 
-    void putConstructorSubinit(const AstClass* classp, AstCFunc* cfuncp, bool top, bool& firstr) {
+    void putConstructorSubinit(const AstClass* classp, AstCFunc* cfuncp, bool top,                std::set<AstClass*> &doneClassesr) {
         for (const AstClassExtends* extp = classp->extendsp(); extp;
              extp = VN_AS(extp->nextp(), ClassExtends)) {
             if (extp->classp()->useVirtualPublic()) {
                 // It's a c++ virtual class (diamond relation)
                 // Must get the subclasses initialized first
-                putConstructorSubinit(extp->classp(), cfuncp, false, firstr);
+                putConstructorSubinit(extp->classp(), cfuncp, false, doneClassesr);
             }
-            puts(firstr ? "" : "\n, ");
-            firstr = false;
+            // Diamond pattern with same base class twice?
+            if (doneClassesr.find(extp->classp()) != doneClassesr.end()) continue;
+            puts(doneClassesr.empty() ? "" : "\n    , ");
+            doneClassesr.emplace(extp->classp());
             puts(prefixNameProtect(extp->classp()));
             if (constructorNeedsProcess(extp->classp())) {
                 puts("(vlProcess, vlSymsp");
@@ -295,8 +297,8 @@ public:
             const AstClass* const classp = VN_CAST(nodep->scopep()->modp(), Class);
             if (nodep->isConstructor() && classp && classp->extendsp()) {
                 puts("\n    : ");
-                bool first = true;
-                putConstructorSubinit(classp, nodep, true, first /*ref*/);
+                std::set<AstClass*> doneClasses;
+                putConstructorSubinit(classp, nodep, true, doneClasses /*ref*/);
             }
         }
         puts(" {\n");
diff --git a/src/V3LinkDot.cpp b/src/V3LinkDot.cpp
index 2d0887306..a8f6a58a7 100644
--- a/src/V3LinkDot.cpp
+++ b/src/V3LinkDot.cpp
@@ -2030,7 +2030,7 @@ class LinkDotResolveVisitor final : public VNVisitor {
     AstNodeFTask* m_ftaskp = nullptr;  // Current function/task
     int m_modportNum = 0;  // Uniqueify modport numbers
     bool m_inSens = false;  // True if in senitem
-    std::set<std::string> m_ifClassImpNames;  // Names imported from interface class
+    std::map<std::string, AstNode*> m_ifClassImpNames;  // Names imported from interface class
     std::set<AstClass*> m_extendsParam;  // Classes that have a parameterized super class
                                          // (except the default instances)
                                          // They are added to the set only in linkDotPrimary.
@@ -2235,9 +2235,9 @@ class LinkDotResolveVisitor final : public VNVisitor {
                                      << "... Location of interface class's function\n"
                                      << interfaceSubp->warnContextSecondary());
                     }
-                    if (!existsInChild
-                        && m_ifClassImpNames.find(interfaceSubp->name())
-                               != m_ifClassImpNames.end()) {
+                    const auto it = m_ifClassImpNames.find(interfaceSubp->name());
+                    if (!existsInChild && it != m_ifClassImpNames.end()
+                        && it->second != interfaceSubp) {  // Not exact same function from diamond
                         implementsClassp->v3error(
                             "Class " << implementsClassp->prettyNameQ() << " implements "
                                      << interfaceClassp->prettyNameQ()
@@ -2249,7 +2249,7 @@ class LinkDotResolveVisitor final : public VNVisitor {
                                      << "... Location of interface class's function\n"
                                      << interfaceSubp->warnContextSecondary());
                     }
-                    m_ifClassImpNames.emplace(interfaceSubp->name());
+                    m_ifClassImpNames.emplace(interfaceSubp->name(), interfaceSubp);
                 }
             }
         }
diff --git a/test_regress/t/t_class_diamond.pl b/test_regress/t/t_class_diamond.pl
new file mode 100755
index 000000000..e64ab41be
--- /dev/null
+++ b/test_regress/t/t_class_diamond.pl
@@ -0,0 +1,21 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# 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
+
+scenarios(simulator => 1);
+
+compile(
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+ok(1);
+1;
diff --git a/test_regress/t/t_class_diamond.v b/test_regress/t/t_class_diamond.v
new file mode 100644
index 000000000..b4af229af
--- /dev/null
+++ b/test_regress/t/t_class_diamond.v
@@ -0,0 +1,59 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module class_tb ();
+interface class Ibase;
+   pure virtual function int fn();
+endclass
+
+interface class Ic1 extends Ibase;
+   pure virtual function int fn1();
+endclass
+
+interface class Ic2 extends Ibase;
+   pure virtual function int fn2();
+endclass
+
+interface class Ic3 extends Ic1, Ic2;
+endclass
+
+class Cls implements Ic3;
+   virtual function int fn();
+      return 10;
+   endfunction
+   virtual function int fn1();
+      return 1;
+   endfunction
+   virtual function int fn2();
+      return 2;
+   endfunction
+endclass
+
+   initial begin
+      Cls cls;
+      Ibase ibase;
+      Ic1 ic1;
+      Ic2 ic2;
+      Ic3 ic3;
+      cls = new;
+      if (cls.fn() != 10) $stop;
+      if (cls.fn1() != 1) $stop;
+      if (cls.fn2() != 2) $stop;
+      ibase = cls;
+      ic1 = cls;
+      ic2 = cls;
+      ic3 = cls;
+      if (ibase.fn() != 10) $stop;
+      if (ic1.fn() != 10) $stop;
+      if (ic2.fn() != 10) $stop;
+      if (ic3.fn() != 10) $stop;
+      if (ic1.fn1() != 1) $stop;
+      if (ic2.fn2() != 2) $stop;
+      $write("*-* All Finished *-*\n");
+      $finish;
+   end
+
+endmodule
diff --git a/test_regress/t/t_implements_collision_bad.v b/test_regress/t/t_implements_collision_bad.v
index d457be661..9767d8677 100644
--- a/test_regress/t/t_implements_collision_bad.v
+++ b/test_regress/t/t_implements_collision_bad.v
@@ -19,6 +19,24 @@ endclass
 class Cls implements IclsBoth;
 endclass
 
+
+// This is not a collision - diamond
+interface class Ibase;
+   pure virtual function int fn();
+endclass
+
+interface class Ic1 extends Ibase;
+   pure virtual function int fn1();
+endclass
+
+interface class Ic2 extends Ibase;
+   pure virtual function int fn2();
+endclass
+
+interface class Ic3 extends Ic1, Ic2;
+endclass
+
+
 module t (/*AUTOARG*/);
    Cls c;
 endmodule