diff --git a/src/library/compiler/ir_interpreter.cpp b/src/library/compiler/ir_interpreter.cpp
index 7c7b21ccb7..19c82d12b1 100644
--- a/src/library/compiler/ir_interpreter.cpp
+++ b/src/library/compiler/ir_interpreter.cpp
@@ -809,7 +809,7 @@ class interpreter {
             }
         } else {
             if (decl_tag(e.m_decl) == decl_kind::Extern) {
-                throw exception(sstream() << "unexpected external declaration '" << fn << "'");
+                throw exception(sstream() << "could not find native implementation of external declaration '" << fn << "'");
             }
             // evaluate args in old stack frame
             for (const auto & arg : args) {