diff --git a/src/resolve/common.cpp b/src/resolve/common.cpp
index e02fe76c..a04e0640 100644
--- a/src/resolve/common.cpp
+++ b/src/resolve/common.cpp
@@ -15,6 +15,15 @@
 #include <expand/cfg.hpp>
 #include <synext_macro.hpp>
 
+::std::ostream& operator<<(::std::ostream& os, ResolveNamespace ns) {
+    switch(ns) {
+    case ResolveNamespace::Namespace:   return os << "Namespace";
+    case ResolveNamespace::Value:   return os << "Value";
+    case ResolveNamespace::Macro:   return os << "Macro";
+    }
+    return os << "?";
+}
+
 namespace {
 
     ResolveItemRef_Type as_Namespace(ResolveItemRef ir) {
diff --git a/src/resolve/common.hpp b/src/resolve/common.hpp
index 82a1961b..a862932f 100644
--- a/src/resolve/common.hpp
+++ b/src/resolve/common.hpp
@@ -65,14 +65,7 @@ enum class ResolveNamespace
     Value,
     Macro,
 };
-static inline ::std::ostream& operator<<(::std::ostream& os, ResolveNamespace ns) {
-    switch(ns) {
-    case ResolveNamespace::Namespace:   return os << "Namespace";
-    case ResolveNamespace::Value:   return os << "Value";
-    case ResolveNamespace::Macro:   return os << "Macro";
-    }
-    return os << "?";
-}
+extern ::std::ostream& operator<<(::std::ostream& os, ResolveNamespace ns);
 
 /// <summary>
 /// Obtain a reference to the module pointed to by `path` (relative to `base_path`)