diff --git a/NEWS.md b/NEWS.md
index b1f211a8ae7..36f55745bc9 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -60,6 +60,7 @@ milestone for 4.0.0
 * _pgr_dijkstra(text,anyarray,anyarray,boolean,boolean,boolean,bigint)
 * _pgr_dijkstra(text,text,boolean,boolean,boolean)
 * _pgr_drivingdistance(text,anyarray,double precision,boolean,boolean)
+* _pgr_kruskal(text,anyarray,text,bigint,double precision)
 * _pgr_prim(text,anyarray,text,bigint,double precision)
 * _pgr_trsp(text,integer,double precision,integer,double precision,boolean,boolean,text)
 * _pgr_trsp(text,text,anyarray,anyarray,boolean)
@@ -75,6 +76,7 @@ milestone for 4.0.0
 **Deprecation of internal C/C++ functions**
 
 * _pgr_drivingdistance(text,anyarray,double precision,boolean,boolean)
+* _pgr_kruskal(text,anyarray,text,bigint,double precision)
 * _pgr_prim(text,anyarray,text,bigint,double precision)
 
 **Internal C/C++ functions in legacy**
diff --git a/doc/src/release_notes.rst b/doc/src/release_notes.rst
index 5f80e3c95ae..90bac91cc93 100644
--- a/doc/src/release_notes.rst
+++ b/doc/src/release_notes.rst
@@ -91,6 +91,7 @@ milestone for 4.0.0
 * _pgr_dijkstra(text,anyarray,anyarray,boolean,boolean,boolean,bigint)
 * _pgr_dijkstra(text,text,boolean,boolean,boolean)
 * _pgr_drivingdistance(text,anyarray,double precision,boolean,boolean)
+* _pgr_kruskal(text,anyarray,text,bigint,double precision)
 * _pgr_prim(text,anyarray,text,bigint,double precision)
 * _pgr_trsp(text,integer,double precision,integer,double precision,boolean,boolean,text)
 * _pgr_trsp(text,text,anyarray,anyarray,boolean)
@@ -106,6 +107,7 @@ milestone for 4.0.0
 .. rubric:: Deprecation of internal C/C++ functions
 
 * _pgr_drivingdistance(text,anyarray,double precision,boolean,boolean)
+* _pgr_kruskal(text,anyarray,text,bigint,double precision)
 * _pgr_prim(text,anyarray,text,bigint,double precision)
 
 .. rubric:: Internal C/C++ functions in legacy
diff --git a/sql/sigs/pgrouting--4.0.sig b/sql/sigs/pgrouting--4.0.sig
index 942756b0e91..7159a7cc85e 100644
--- a/sql/sigs/pgrouting--4.0.sig
+++ b/sql/sigs/pgrouting--4.0.sig
@@ -184,7 +184,6 @@ pgr_kruskaldd(text,bigint,numeric)
 pgr_kruskaldfs(text,anyarray,bigint)
 pgr_kruskaldfs(text,bigint,bigint)
 pgr_kruskal(text)
-_pgr_kruskal(text,anyarray,text,bigint,double precision)
 _pgr_kruskalv4(text,anyarray,text,bigint,double precision)
 pgr_ksp(text,anyarray,anyarray,integer,boolean,boolean)
 _pgr_ksp(text,anyarray,anyarray,integer,boolean,boolean,boolean)
diff --git a/sql/spanningTree/_kruskal.sql b/sql/spanningTree/_kruskal.sql
index 8842258bfb1..cbddb46d5ef 100644
--- a/sql/spanningTree/_kruskal.sql
+++ b/sql/spanningTree/_kruskal.sql
@@ -53,29 +53,3 @@ LANGUAGE C VOLATILE STRICT;
 
 COMMENT ON FUNCTION _pgr_kruskalv4(TEXT, ANYARRAY, TEXT, BIGINT, FLOAT)
 IS 'pgRouting internal function';
-
---v3.0
-CREATE FUNCTION _pgr_kruskal(
-    TEXT,             -- Edge sql
-    ANYARRAY,         -- tree root for traversal
-    fn_suffix TEXT,
-    max_depth BIGINT,
-    distance FLOAT,
-
-    OUT seq BIGINT,
-    OUT depth BIGINT,
-    OUT start_vid BIGINT,
-    OUT node BIGINT,
-    OUT edge BIGINT,
-    OUT cost FLOAT,
-    OUT agg_cost FLOAT)
-RETURNS SETOF RECORD AS
-'MODULE_PATHNAME'
-LANGUAGE C VOLATILE STRICT;
-
-
--- COMMENTS
-
-
-COMMENT ON FUNCTION _pgr_kruskal(TEXT, ANYARRAY, TEXT, BIGINT, FLOAT)
-IS 'pgRouting internal function deprecated on v3.7.0';
diff --git a/src/spanningTree/kruskal.c b/src/spanningTree/kruskal.c
index 7e0d11c8880..aa5bb47dfa9 100644
--- a/src/spanningTree/kruskal.c
+++ b/src/spanningTree/kruskal.c
@@ -170,7 +170,11 @@ PGDLLEXPORT Datum _pgr_kruskalv4(PG_FUNCTION_ARGS) {
     }
 }
 
-/***********************************************************************************/
+/* Deprecated code starts here
+ * This code is used on v3.6 and under
+ *
+ * TODO(v5) Move to legacy
+ */
 
 PGDLLEXPORT Datum _pgr_kruskal(PG_FUNCTION_ARGS);
 PG_FUNCTION_INFO_V1(_pgr_kruskal);
@@ -182,6 +186,12 @@ PGDLLEXPORT Datum _pgr_kruskal(PG_FUNCTION_ARGS) {
     MST_rt *result_tuples = NULL;
     size_t result_count = 0;
 
+    ereport(NOTICE, (
+            errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+            errmsg("A stored procedure is using deprecated C internal function '%s'", __func__),
+            errdetail("Library function '%s' was deprecated in pgRouting %s", __func__, "3.7.0"),
+            errhint("Consider upgrade pgRouting")));
+
     if (SRF_IS_FIRSTCALL()) {
         MemoryContext   oldcontext;
         funcctx = SRF_FIRSTCALL_INIT();