diff --git a/src/Expr.cc b/src/Expr.cc
index 6d08955113..237ca1faa6 100644
--- a/src/Expr.cc
+++ b/src/Expr.cc
@@ -274,14 +274,7 @@ void Expr::AssignToIndex(ValPtr v1, ValPtr v2, ValPtr v3) const
 	                                 iterators_invalidated);
 
 	if ( iterators_invalidated )
-		{
-		ODesc d;
-		Describe(&d);
-		reporter->PushLocation(GetLocationInfo());
-		reporter->Warning("possible loop/iterator invalidation caused by expression: %s",
-		                  d.Description());
-		reporter->PopLocation();
-		}
+		reporter->ExprRuntimeWarning(this, "possible loop/iterator invalidation");
 
 	if ( error_msg )
 		RuntimeErrorWithCallStack(error_msg);
@@ -2974,14 +2967,7 @@ void IndexExpr::Add(Frame* f)
 	v1->AsTableVal()->Assign(std::move(v2), nullptr, true, &iterators_invalidated);
 
 	if ( iterators_invalidated )
-		{
-		ODesc d;
-		Describe(&d);
-		reporter->PushLocation(GetLocationInfo());
-		reporter->Warning("possible loop/iterator invalidation caused by expression: %s",
-		                  d.Description());
-		reporter->PopLocation();
-		}
+		reporter->ExprRuntimeWarning(this, "possible loop/iterator invalidation");
 	}
 
 void IndexExpr::Delete(Frame* f)
@@ -3003,14 +2989,7 @@ void IndexExpr::Delete(Frame* f)
 	v1->AsTableVal()->Remove(*v2, true, &iterators_invalidated);
 
 	if ( iterators_invalidated )
-		{
-		ODesc d;
-		Describe(&d);
-		reporter->PushLocation(GetLocationInfo());
-		reporter->Warning("possible loop/iterator invalidation caused by expression: %s",
-		                  d.Description());
-		reporter->PopLocation();
-		}
+		reporter->ExprRuntimeWarning(this, "possible loop/iterator invalidation");
 	}
 
 ExprPtr IndexExpr::MakeLvalue()
diff --git a/src/Reporter.cc b/src/Reporter.cc
index 0ed84562e7..145bce4aea 100644
--- a/src/Reporter.cc
+++ b/src/Reporter.cc
@@ -174,6 +174,21 @@ void Reporter::ExprRuntimeError(const detail::Expr* expr, const char* fmt, ...)
 	throw InterpreterException();
 	}
 
+void Reporter::ExprRuntimeWarning(const detail::Expr* expr, const char* fmt, ...)
+	{
+	ODesc d;
+	expr->Describe(&d);
+
+	PushLocation(expr->GetLocationInfo());
+	va_list ap;
+	va_start(ap, fmt);
+	FILE* out = EmitToStderr(warnings_to_stderr) ? stderr : nullptr;
+	DoLog("expression warning", reporter_warning, out, nullptr, nullptr, true, true,
+	      d.Description(), fmt, ap);
+	va_end(ap);
+	PopLocation();
+	}
+
 void Reporter::RuntimeError(const detail::Location* location, const char* fmt, ...)
 	{
 	++errors;
diff --git a/src/Reporter.h b/src/Reporter.h
index c52d54f8b2..be5515ee11 100644
--- a/src/Reporter.h
+++ b/src/Reporter.h
@@ -112,6 +112,10 @@ public:
 	[[noreturn]] void RuntimeError(const detail::Location* location, const char* fmt, ...)
 		__attribute__((format(printf, 3, 4)));
 
+	// Report a rutnime warning in evaluating a Zeek script expression.
+	void ExprRuntimeWarning(const detail::Expr* expr, const char* fmt, ...)
+		__attribute__((format(printf, 3, 4)));
+
 	// Report a runtime error in executing a compiled script. This
 	// function will not return but raise an InterpreterException.
 	[[noreturn]] void CPPRuntimeError(const char* fmt, ...) __attribute__((format(printf, 2, 3)));
diff --git a/testing/btest/Baseline/language.table-set-iterator-invalidation/err b/testing/btest/Baseline/language.table-set-iterator-invalidation/err
index e33c980fc3..238b43773d 100644
--- a/testing/btest/Baseline/language.table-set-iterator-invalidation/err
+++ b/testing/btest/Baseline/language.table-set-iterator-invalidation/err
@@ -1,5 +1,5 @@
 ### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
-warning in <...>/table-set-iterator-invalidation.zeek, line 22: possible loop/iterator invalidation caused by expression: t[4]
-warning in <...>/table-set-iterator-invalidation.zeek, line 31: possible loop/iterator invalidation caused by expression: t[4]
-warning in <...>/table-set-iterator-invalidation.zeek, line 54: possible loop/iterator invalidation caused by expression: s[4]
-warning in <...>/table-set-iterator-invalidation.zeek, line 63: possible loop/iterator invalidation caused by expression: s[4]
+expression warning in <...>/table-set-iterator-invalidation.zeek, line 22: possible loop/iterator invalidation (t[4])
+expression warning in <...>/table-set-iterator-invalidation.zeek, line 31: possible loop/iterator invalidation (t[4])
+expression warning in <...>/table-set-iterator-invalidation.zeek, line 54: possible loop/iterator invalidation (s[4])
+expression warning in <...>/table-set-iterator-invalidation.zeek, line 63: possible loop/iterator invalidation (s[4])