diff --git a/include/verilated.cpp b/include/verilated.cpp
index 4370a5b75..38ecdf221 100644
--- a/include/verilated.cpp
+++ b/include/verilated.cpp
@@ -2836,7 +2836,7 @@ const char* Verilated::productVersion() VL_PURE { return VERILATOR_VERSION; }
 void Verilated::nullPointerError(const char* filename, int linenum) VL_MT_SAFE {
     // Slowpath - Called only on error
     VL_FATAL_MT(filename, linenum, "", "Null pointer dereferenced");
-    VL_UNREACHABLE
+    VL_UNREACHABLE;
 }
 
 void Verilated::overWidthError(const char* signame) VL_MT_SAFE {
@@ -2844,7 +2844,7 @@ void Verilated::overWidthError(const char* signame) VL_MT_SAFE {
     const std::string msg = (std::string{"Testbench C set input '"} + signame
                              + "' to value that overflows what the signal's width can fit");
     VL_FATAL_MT("unknown", 0, "", msg.c_str());
-    VL_UNREACHABLE
+    VL_UNREACHABLE;
 }
 
 void Verilated::mkdir(const char* dirname) VL_MT_UNSAFE {
diff --git a/include/verilatedos.h b/include/verilatedos.h
index 2e1456852..d4d64ea96 100644
--- a/include/verilatedos.h
+++ b/include/verilatedos.h
@@ -69,9 +69,9 @@
 #  define VL_EXCLUDES(x) __attribute__((locks_excluded(x)))
 #  define VL_SCOPED_CAPABILITY __attribute__((scoped_lockable))
 # endif
-# define VL_LIKELY(x) __builtin_expect(!!(x), 1)
-# define VL_UNLIKELY(x) __builtin_expect(!!(x), 0)
-# define VL_UNREACHABLE __builtin_unreachable();
+# define VL_LIKELY(x) __builtin_expect(!!(x), 1)  // Prefer over C++20 [[likely]]
+# define VL_UNLIKELY(x) __builtin_expect(!!(x), 0)  // Prefer over C++20 [[unlikely]]
+# define VL_UNREACHABLE __builtin_unreachable()  // C++23 std::unreachable()
 # define VL_PREFETCH_RD(p) __builtin_prefetch((p), 0)
 # define VL_PREFETCH_RW(p) __builtin_prefetch((p), 1)
 #endif
diff --git a/src/V3Ast.cpp b/src/V3Ast.cpp
index 1bd1ab6b9..27b52f353 100644
--- a/src/V3Ast.cpp
+++ b/src/V3Ast.cpp
@@ -1187,7 +1187,7 @@ void AstNode::dumpTreeDotFile(const string& filename, bool append, bool doDump)
 void AstNode::v3errorEndFatal(std::ostringstream& str) const {
     v3errorEnd(str);
     assert(0);  // LCOV_EXCL_LINE
-    VL_UNREACHABLE
+    VL_UNREACHABLE;
 }
 
 string AstNode::instanceStr() const {
diff --git a/src/V3Error.h b/src/V3Error.h
index d5be7e005..d103866d6 100644
--- a/src/V3Error.h
+++ b/src/V3Error.h
@@ -330,7 +330,7 @@ inline void v3errorEnd(std::ostringstream& sstr) { V3Error::v3errorEnd(sstr); }
 inline void v3errorEndFatal(std::ostringstream& sstr) {
     V3Error::v3errorEnd(sstr);
     assert(0);  // LCOV_EXCL_LINE
-    VL_UNREACHABLE
+    VL_UNREACHABLE;
 }
 
 // Theses allow errors using << operators: v3error("foo"<<"bar");
diff --git a/src/V3FileLine.h b/src/V3FileLine.h
index 0737b0783..f6c53bfb1 100644
--- a/src/V3FileLine.h
+++ b/src/V3FileLine.h
@@ -307,7 +307,7 @@ public:
     void v3errorEndFatal(std::ostringstream& str) VL_ATTR_NORETURN {
         v3errorEnd(str);
         assert(0);  // LCOV_EXCL_LINE
-        VL_UNREACHABLE
+        VL_UNREACHABLE;
     }
     /// When building an error, prefix for printing continuation lines
     /// e.g. information referring to the same FileLine as before
diff --git a/src/V3Graph.cpp b/src/V3Graph.cpp
index faffb7b41..4218394fa 100644
--- a/src/V3Graph.cpp
+++ b/src/V3Graph.cpp
@@ -144,7 +144,7 @@ void V3GraphVertex::v3errorEnd(std::ostringstream& str) const {
 void V3GraphVertex::v3errorEndFatal(std::ostringstream& str) const {
     v3errorEnd(str);
     assert(0);  // LCOV_EXCL_LINE
-    VL_UNREACHABLE
+    VL_UNREACHABLE;
 }
 
 std::ostream& operator<<(std::ostream& os, V3GraphVertex* vertexp) {
diff --git a/src/V3Number.cpp b/src/V3Number.cpp
index 3dcfc88e2..00e7b1524 100644
--- a/src/V3Number.cpp
+++ b/src/V3Number.cpp
@@ -91,7 +91,7 @@ void V3Number::v3errorEnd(std::ostringstream& str) const {
 void V3Number::v3errorEndFatal(std::ostringstream& str) const {
     v3errorEnd(str);
     assert(0);  // LCOV_EXCL_LINE
-    VL_UNREACHABLE
+    VL_UNREACHABLE;
 }
 
 //======================================================================