diff --git a/compiler/lookups.nim b/compiler/lookups.nim
index afa2716d8ac5f..6301368986e27 100644
--- a/compiler/lookups.nim
+++ b/compiler/lookups.nim
@@ -566,7 +566,11 @@ proc errorUndeclaredIdentifier*(c: PContext; info: TLineInfo; name: string, extr
   if name == "_":
     err = "the special identifier '_' is ignored in declarations and cannot be used"
   else:
-    err = "undeclared identifier: '" & name & "'" & extra
+    err = "undeclared identifier: '" & name & "'"
+    if "`gensym" in name:
+      err.add "; if declared in a template, this identifier may be inconsistently marked inject or gensym"
+    if extra.len != 0:
+      err.add extra
     if c.recursiveDep.len > 0:
       err.add "\nThis might be caused by a recursive module dependency:\n"
       err.add c.recursiveDep
diff --git a/compiler/semtempl.nim b/compiler/semtempl.nim
index 36b7838ec6f13..871a10db98790 100644
--- a/compiler/semtempl.nim
+++ b/compiler/semtempl.nim
@@ -260,7 +260,7 @@ proc semRoutineInTemplName(c: var TemplCtx, n: PNode): PNode =
   if n.kind == nkIdent:
     let s = qualifiedLookUp(c.c, n, {})
     if s != nil:
-      if s.owner == c.owner and (s.kind == skParam or sfGenSym in s.flags):
+      if s.owner == c.owner and s.kind == skParam:
         incl(s.flags, sfUsed)
         result = newSymNode(s, n.info)
         onUse(n.info, s)
diff --git a/testament/important_packages.nim b/testament/important_packages.nim
index 462bf8a30d28f..65f48d5537493 100644
--- a/testament/important_packages.nim
+++ b/testament/important_packages.nim
@@ -60,7 +60,7 @@ pkg "compactdict"
 pkg "comprehension", "nimble test", "https://github.com/alehander92/comprehension"
 pkg "cowstrings"
 pkg "criterion", allowFailure = true # needs testing binary
-pkg "datamancer"
+pkg "datamancer", "nimble install -y arraymancer@#HEAD; nimble test"
 pkg "dashing", "nim c tests/functional.nim"
 pkg "delaunay"
 pkg "docopt"
@@ -72,7 +72,7 @@ pkg "fragments", "nim c -r fragments/dsl.nim", allowFailure = true # pending htt
 pkg "fusion"
 pkg "gara"
 pkg "glob"
-pkg "ggplotnim", "nim c -d:noCairo -r tests/tests.nim"
+pkg "ggplotnim", "nimble install -y arraymancer@#HEAD; nim c -d:noCairo -r tests/tests.nim"
 pkg "gittyup", "nimble test", "https://github.com/disruptek/gittyup", allowFailure = true
 pkg "gnuplot", "nim c gnuplot.nim"
 # pkg "gram", "nim c -r --mm:arc --define:danger tests/test.nim", "https://github.com/disruptek/gram"
@@ -124,7 +124,7 @@ pkg "nimx", "nim c test/main.nim", allowFailure = true
 pkg "nitter", "nim c src/nitter.nim", "https://github.com/zedeus/nitter"
 pkg "norm", "testament r tests/common/tmodel.nim"
 pkg "npeg", "nimble testarc"
-pkg "numericalnim", "nimble nimCI"
+pkg "numericalnim", "nimble install -y arraymancer@#HEAD; nimble nimCI"
 pkg "optionsutils"
 pkg "ormin", "nim c -o:orminn ormin.nim"
 pkg "parsetoml"
diff --git a/tests/errmsgs/tinconsistentgensym.nim b/tests/errmsgs/tinconsistentgensym.nim
new file mode 100644
index 0000000000000..026c17fcaa202
--- /dev/null
+++ b/tests/errmsgs/tinconsistentgensym.nim
@@ -0,0 +1,25 @@
+discard """
+  cmd: "nim check --hints:off $file"
+"""
+
+block:
+  template foo =
+    when false:
+      let x = 123
+    else:
+      template x: untyped = 456
+    echo x #[tt.Error
+         ^ undeclared identifier: 'x`gensym0'; if declared in a template, this identifier may be inconsistently marked inject or gensym]#
+  foo()
+
+block:
+  template foo(y: static bool) =
+    block:
+      when y:
+        let x {.gensym.} = 123
+      else:
+        let x {.inject.} = 456
+      echo x #[tt.Error
+           ^ undeclared identifier: 'x']#
+  foo(false)
+  foo(true)
diff --git a/tests/template/tgensymhijack.nim b/tests/template/tgensymhijack.nim
new file mode 100644
index 0000000000000..72ff3d49571b2
--- /dev/null
+++ b/tests/template/tgensymhijack.nim
@@ -0,0 +1,37 @@
+# issue #23326
+
+type Result*[E] = object
+  e*: E
+
+proc error*[E](v: Result[E]): E = discard
+
+template valueOr*[E](self: Result[E], def: untyped): int =
+  when E isnot void:
+    when false:
+      # Comment line below to make it work
+      template error(): E {.used, gensym.} = s.e
+      discard
+    else:
+      template error(): E {.used, inject.} =
+        self.e
+
+      def
+  else:
+    def
+
+
+block:
+  let rErr = Result[string](e: "a")
+  let rErrV = rErr.valueOr:
+    ord(error[0])
+
+block:
+  template foo(x: static bool): untyped =
+    when x:
+      let a = 123
+    else:
+      template a: untyped {.gensym.} = 456
+    a
+  
+  doAssert foo(false) == 456
+  doAssert foo(true) == 123