diff --git a/compiler/semtypes.nim b/compiler/semtypes.nim
index 0fce7b417..b34dc36e3 100644
--- a/compiler/semtypes.nim
+++ b/compiler/semtypes.nim
@@ -10,7 +10,7 @@
 # this module does the semantic checking of type declarations
 # included from sem.nim
 
-import math
+import std/math
 
 const
   errStringOrIdentNodeExpected = "string or ident node expected"
@@ -1171,6 +1171,7 @@ proc liftParamType(c: PContext, procKind: TSymKind, genericParams: PNode,
   else: discard
 
 proc semParamType(c: PContext, n: PNode, constraint: var PNode): PType =
+  ## Semchecks the type of parameters.
   if n.kind == nkCurlyExpr:
     result = semTypeNode(c, n[0], nil)
     constraint = semNodeKindConstraints(n, c.config, 1)
@@ -1226,10 +1227,11 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
     if hasType:
       typ = semParamType(c, a[^2], constraint)
       # TODO: Disallow typed/untyped in procs in the compiler/stdlib
-      if kind == skProc and (typ.kind == tyTyped or typ.kind == tyUntyped):
+      if kind in {skProc, skFunc} and (typ.kind == tyTyped or typ.kind == tyUntyped):
         if not isMagic(getCurrOwner(c)):
           localError(c.config, a[^2].info, "'" & typ.sym.name.s & "' is only allowed in templates and macros or magic procs")
 
+
     if hasDefault:
       def = a[^1]
       block determineType:
diff --git a/compiler/typeallowed.nim b/compiler/typeallowed.nim
index db3735359..9075d9e38 100644
--- a/compiler/typeallowed.nim
+++ b/compiler/typeallowed.nim
@@ -57,7 +57,8 @@ proc typeAllowedAux(marker: var IntSet, typ: PType, kind: TSymKind,
   of tyVar, tyLent:
     if kind in {skProc, skFunc, skConst} and (views notin c.features):
       result = t
-    elif t.kind == tyLent and kind != skResult and (views notin c.features):
+    elif t.kind == tyLent and ((kind != skResult and views notin c.features) or
+                              kind == skParam): # lent can't be used as parameters.
       result = t
     else:
       var t2 = skipTypes(t[0], abstractInst-{tyTypeDesc, tySink})
diff --git a/tests/lent/t16898.nim b/tests/lent/t16898.nim
new file mode 100644
index 000000000..ea7c934ef
--- /dev/null
+++ b/tests/lent/t16898.nim
@@ -0,0 +1,31 @@
+discard """
+  errormsg: "invalid type: 'lent QuadraticExt' in this context: 'proc (r: var QuadraticExt, a: lent QuadraticExt, b: lent QuadraticExt){.noSideEffect, gcsafe, locks: 0.}' for proc"
+"""
+
+# bug #16898
+type
+  Fp[N: static int, T] = object
+    big: array[N, T]
+
+type
+  QuadraticExt* = concept x
+    ## Quadratic Extension concept (like complex)
+    type BaseField = auto
+    x.c0 is BaseField
+    x.c1 is BaseField
+
+{.experimental:"views".}
+
+func prod(r: var QuadraticExt, a, b: lent QuadraticExt) =
+  discard
+
+type
+  Fp2[N: static int, T] = object
+    c0, c1: Fp[N, T]
+
+# This should be passed by reference,
+# but concepts do not respect the 24 bytes rule
+# or `byref` pragma.
+var r, a, b: Fp2[6, uint64]
+
+prod(r, a, b)
diff --git a/tests/lent/t17621.nim b/tests/lent/t17621.nim
new file mode 100644
index 000000000..e324a963e
--- /dev/null
+++ b/tests/lent/t17621.nim
@@ -0,0 +1,15 @@
+discard """
+  errormsg: "invalid type: 'lent Test' in this context: 'proc (self: lent Test)' for proc"
+"""
+
+# bug #17621
+{.experimental: "views".}
+
+type Test = ref object
+  foo: int
+
+proc modify(self: lent Test) =
+  self.foo += 1
+
+let test = Test(foo: 12)
+modify(test)