diff --git a/hilti/runtime/include/exception.h b/hilti/runtime/include/exception.h
index 433e82a3b..4af20e18e 100644
--- a/hilti/runtime/include/exception.h
+++ b/hilti/runtime/include/exception.h
@@ -3,6 +3,7 @@
 #pragma once
 
 #include <iostream>
+#include <memory>
 #include <ostream>
 #include <stdexcept>
 #include <string>
@@ -24,18 +25,43 @@ class Exception : public std::runtime_error {
     /**
      * @param desc message describing the situation
      */
-    Exception(const std::string& desc) : Exception(Internal(), "Exception", desc) {}
+    Exception(const std::string& desc) : Exception(Internal(), "Exception", desc) {
+#ifndef NDEBUG
+        _backtrace = std::make_unique<Backtrace>();
+#endif
+    }
 
     /**
      * @param desc message describing the situation
      * @param location string indicating the location of the operation that failed
      */
-    Exception(std::string_view desc, std::string_view location) : Exception(Internal(), "Exception", desc, location) {}
+    Exception(std::string_view desc, std::string_view location) : Exception(Internal(), "Exception", desc, location) {
+#ifndef NDEBUG
+        _backtrace = std::make_unique<Backtrace>();
+#endif
+    }
 
     Exception();
-    Exception(const Exception&) = default;
+
+    Exception(const Exception& other)
+        : std::runtime_error(other), _description(other._description), _location(other._location) {
+        if ( other._backtrace )
+            _backtrace = std::make_unique<Backtrace>(*other._backtrace);
+    }
+
     Exception(Exception&&) noexcept = default;
-    Exception& operator=(const Exception&) = default;
+    Exception& operator=(const Exception& other) {
+        // Note: We don't copy the backtrace here, as it's not clear what
+        // that would mean.
+        if ( &other != this ) {
+            std::runtime_error::operator=(other);
+            _description = other._description;
+            _location = other._location;
+        }
+
+        return *this;
+    }
+
     Exception& operator=(Exception&&) noexcept = default;
 
     // Empty, but required to make exception handling work between library
@@ -51,9 +77,9 @@ class Exception : public std::runtime_error {
 
     /**
      * Returns a stack backtrace captured at the time the exception was
-     * thrown.
+     * thrown, if available. Returns null if not available.
      */
-    auto backtrace() const { return _backtrace.backtrace(); }
+    auto backtrace() const { return _backtrace.get(); }
 
 protected:
     enum Internal {};
@@ -66,7 +92,7 @@ class Exception : public std::runtime_error {
 
     std::string _description;
     std::string _location;
-    Backtrace _backtrace;
+    std::unique_ptr<Backtrace> _backtrace; // null if not available
 };
 
 inline std::ostream& operator<<(std::ostream& stream, const Exception& e) { return stream << e.what(); }
diff --git a/hilti/runtime/src/configuration.cc b/hilti/runtime/src/configuration.cc
index 9633cb4eb..2abc400c6 100644
--- a/hilti/runtime/src/configuration.cc
+++ b/hilti/runtime/src/configuration.cc
@@ -24,5 +24,10 @@ void configuration::set(Configuration cfg) {
     if ( isInitialized() )
         hilti::rt::fatalError("attempt to change configuration after library has already been initialized");
 
+#ifndef NDEBUG
+    if ( cfg.show_backtraces )
+        hilti::rt::warning("printing of exception backtraces enabled, but not supported in release builds");
+#endif
+
     *detail::__configuration = std::move(cfg);
 }
diff --git a/hilti/runtime/src/exception.cc b/hilti/runtime/src/exception.cc
index 1a30eee0f..9c8d878cf 100644
--- a/hilti/runtime/src/exception.cc
+++ b/hilti/runtime/src/exception.cc
@@ -44,7 +44,10 @@ static void printException(const std::string& msg, const Exception& e, std::ostr
     if ( ! configuration::get().show_backtraces )
         return;
 
-    auto bt = e.backtrace();
+    if ( ! e.backtrace() )
+        return;
+
+    auto bt = e.backtrace()->backtrace();
     if ( bt->empty() )
         return;
 
diff --git a/hilti/runtime/src/tests/exception.cc b/hilti/runtime/src/tests/exception.cc
index 0eb60cb86..91fcbcfce 100644
--- a/hilti/runtime/src/tests/exception.cc
+++ b/hilti/runtime/src/tests/exception.cc
@@ -61,8 +61,13 @@ TEST_CASE("backtrace") {
     // - two frames from doctest's expansion of `CHECK_EQ`, and
     // - one frame for the current line
     // - three frames from the test harness to reach and expand `TEST_CASE`.
-#ifdef HILTI_HAVE_BACKTRACE
-    CHECK_GE(Exception("description").backtrace()->size(), 7U);
+#ifndef NDEBUG
+#if defined(HILTI_HAVE_BACKTRACE)
+    CHECK_GE(Exception("description").backtrace()->backtrace()->size(), 7U);
+#endif
+#else
+    // No backtrace captured in release builds.
+    CHECK(! Exception("description").backtrace());
 #endif
 }
 
diff --git a/hilti/toolchain/src/compiler/driver.cc b/hilti/toolchain/src/compiler/driver.cc
index 2c95a5792..876370d56 100644
--- a/hilti/toolchain/src/compiler/driver.cc
+++ b/hilti/toolchain/src/compiler/driver.cc
@@ -1167,14 +1167,20 @@ Result<Nothing> Driver::jitUnits() {
 void Driver::printHiltiException(const hilti::rt::Exception& e) {
     std::cerr << fmt("uncaught exception %s: %s", util::demangle(typeid(e).name()), e.what()) << std::endl;
 
-    if ( _driver_options.show_backtraces ) {
-        if ( auto bt = e.backtrace(); ! bt->empty() ) {
-            std::cerr << "backtrace:\n";
+    if ( ! _driver_options.show_backtraces )
+        return;
 
-            for ( const auto& s : *bt )
-                std::cerr << "  " << s << "\n";
-        }
-    }
+    if ( ! e.backtrace() )
+        return;
+
+    auto bt = e.backtrace()->backtrace();
+    if ( bt->empty() )
+        return;
+
+    std::cerr << "backtrace:\n";
+
+    for ( const auto& s : *bt )
+        std::cerr << "  " << s << "\n";
 }
 
 Result<Nothing> Driver::initRuntime() {