diff --git a/src/Attr.cc b/src/Attr.cc
index a32cc89668..c464be6f54 100644
--- a/src/Attr.cc
+++ b/src/Attr.cc
@@ -40,6 +40,18 @@ Attr::Attr(AttrTag t)
 void Attr::SetAttrExpr(ExprPtr e)
 	{ expr = std::move(e); }
 
+std::string Attr::DeprecationMessage() const
+	{
+	if ( tag != ATTR_DEPRECATED )
+		return "";
+
+	if ( ! expr )
+		return "";
+
+	auto ce = static_cast<zeek::detail::ConstExpr*>(expr.get());
+	return ce->Value()->AsStringVal()->CheckString();
+	}
+
 void Attr::Describe(ODesc* d) const
 	{
 	AddTag(d);
diff --git a/src/Attr.h b/src/Attr.h
index 4439701f86..2c9d278a73 100644
--- a/src/Attr.h
+++ b/src/Attr.h
@@ -3,6 +3,7 @@
 #pragma once
 
 #include <vector>
+#include <string>
 
 #include "Obj.h"
 #include "BroList.h"
@@ -73,6 +74,12 @@ public:
 	void Describe(ODesc* d) const override;
 	void DescribeReST(ODesc* d, bool shorten = false) const;
 
+	/**
+	 * Returns the deprecation string associated with a &deprecated attribute
+	 * or an empty string if this is not such an attribute.
+	 */
+	std::string DeprecationMessage() const;
+
 	bool operator==(const Attr& other) const
 		{
 		if ( tag != other.tag )
diff --git a/src/ID.cc b/src/ID.cc
index ba184ccaec..1b8c3fef58 100644
--- a/src/ID.cc
+++ b/src/ID.cc
@@ -294,14 +294,7 @@ std::string ID::GetDeprecationWarning() const
 	const auto& depr_attr = GetAttr(ATTR_DEPRECATED);
 
 	if ( depr_attr )
-		{
-		auto expr = static_cast<zeek::detail::ConstExpr*>(depr_attr->GetExpr().get());
-		if ( expr )
-			{
-			StringVal* text = expr->Value()->AsStringVal();
-			result = text->CheckString();
-			}
-		}
+		result = depr_attr->DeprecationMessage();
 
 	if ( result.empty() )
 		return fmt("deprecated (%s)", Name());
diff --git a/src/Type.cc b/src/Type.cc
index 6a833ddb9e..cb4b1d793f 100644
--- a/src/Type.cc
+++ b/src/Type.cc
@@ -563,7 +563,7 @@ FuncType::FuncType(RecordTypePtr arg_args,
 		offsets[i] = i;
 		}
 
-	prototypes.emplace_back(Prototype{false, args, std::move(offsets)});
+	prototypes.emplace_back(Prototype{false, "", args, std::move(offsets)});
 	}
 
 TypePtr FuncType::ShallowClone()
@@ -1120,14 +1120,7 @@ string RecordType::GetFieldDeprecationWarning(int field, bool has_check) const
 		{
 		string result;
 		if ( const auto& deprecation = decl->GetAttr(zeek::detail::ATTR_DEPRECATED) )
-			{
-			auto expr = static_cast<zeek::detail::ConstExpr*>(deprecation->GetExpr().get());
-			if ( expr )
-				{
-				StringVal* text = expr->Value()->AsStringVal();
-				result = text->CheckString();
-				}
-			}
+			result = deprecation->DeprecationMessage();
 
 		if ( result.empty() )
 			return fmt("deprecated (%s%s$%s)", GetName().c_str(), has_check ? "?" : "",
diff --git a/src/Type.h b/src/Type.h
index b5d58a633c..a2054473d3 100644
--- a/src/Type.h
+++ b/src/Type.h
@@ -427,6 +427,7 @@ public:
 	 */
 	struct Prototype {
 		bool deprecated;
+		std::string deprecation_msg;
 		RecordTypePtr args;
 		std::map<int, int> offsets;
 	};
diff --git a/src/Var.cc b/src/Var.cc
index f7722064f4..535c9ab096 100644
--- a/src/Var.cc
+++ b/src/Var.cc
@@ -100,13 +100,23 @@ static bool add_prototype(const zeek::detail::IDPtr& id, zeek::Type* t,
 		}
 
 	auto deprecated = false;
+	std::string depr_msg;
 
 	if ( attrs )
 		for ( const auto& a : *attrs )
 			if ( a->Tag() == zeek::detail::ATTR_DEPRECATED )
+				{
 				deprecated = true;
+				depr_msg = a->DeprecationMessage();
+				break;
+				}
+
+	zeek::FuncType::Prototype p;
+	p.deprecated = deprecated;
+	p.deprecation_msg = std::move(depr_msg);
+	p.args = alt_args;
+	p.offsets = std::move(offsets);
 
-	zeek::FuncType::Prototype p{deprecated, alt_args, std::move(offsets)};
 	canon_ft->AddPrototype(std::move(p));
 	return true;
 	}
@@ -454,9 +464,19 @@ static std::optional<zeek::FuncType::Prototype> func_type_check(const zeek::Func
 
 	if ( rval )
 		for ( auto i = 0; i < rval->args->NumFields(); ++i )
-			if ( rval->args->FieldDecl(i)->GetAttr(zeek::detail::ATTR_DEPRECATED) )
-				impl->Warn(fmt("use of deprecated parameter '%s'",
-				               rval->args->FieldName(i)), decl, true);
+			if ( auto ad = rval->args->FieldDecl(i)->GetAttr(zeek::detail::ATTR_DEPRECATED) )
+				{
+				auto msg = ad->DeprecationMessage();
+
+				if ( msg.empty() )
+					impl->Warn(fmt("use of deprecated parameter '%s'",
+				                   rval->args->FieldName(i)),
+				               decl, true);
+				else
+					impl->Warn(fmt("use of deprecated parameter '%s': %s",
+				                   rval->args->FieldName(i), msg.data()),
+				               decl, true);
+				}
 
 	return rval;
 	}
@@ -531,8 +551,15 @@ void begin_func(zeek::detail::IDPtr id, const char* module_name,
 				}
 
 			if ( prototype->deprecated )
-				t->Warn(fmt("use of deprecated '%s' prototype", id->Name()),
-				        prototype->args.get(), true);
+				{
+				if ( prototype->deprecation_msg.empty() )
+					t->Warn(fmt("use of deprecated '%s' prototype", id->Name()),
+					        prototype->args.get(), true);
+				else
+					t->Warn(fmt("use of deprecated '%s' prototype: %s",
+					            id->Name(), prototype->deprecation_msg.data()),
+					        prototype->args.get(), true);
+				}
 			}
 		else
 			{
diff --git a/testing/btest/Baseline/language.alternate-prototypes-deprecated-args/out b/testing/btest/Baseline/language.alternate-prototypes-deprecated-args/out
index 0f67248592..8a8d8e5b88 100644
--- a/testing/btest/Baseline/language.alternate-prototypes-deprecated-args/out
+++ b/testing/btest/Baseline/language.alternate-prototypes-deprecated-args/out
@@ -1,5 +1,5 @@
-warning in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 9 and /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 5: use of deprecated parameter 'b' (event(a:string; b:string; c:string;))
-warning in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 19 and /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 7: use of deprecated 'myev' prototype (event(a:string; b:string;))
+warning in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 9 and /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 5: use of deprecated parameter 'b': Don't use 'b' (event(a:string; b:string; c:string;))
+warning in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 19 and /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 7: use of deprecated 'myev' prototype: Don't use this prototype (event(a:string; b:string;))
 myev (canon), one, two, three
 myev (new), one, three
 myev (old), one, two