diff --git a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
index 0f8171fef881..1bd17d6c9778 100644
--- a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -1630,7 +1630,11 @@ object SymDenotations {
       myBaseTypeCachePeriod = Nowhere
     }
 
-    def invalidateMemberCaches(sym: Symbol)(using Context): Unit =
+    def invalidateMemberCaches()(using Context): Unit =
+      myMemberCachePeriod = Nowhere
+      invalidateMemberNamesCache()
+
+    def invalidateMemberCachesFor(sym: Symbol)(using Context): Unit =
       if myMemberCache != null then myMemberCache.remove(sym.name)
       if !sym.flagsUNSAFE.is(Private) then
         invalidateMemberNamesCache()
@@ -1831,7 +1835,7 @@ object SymDenotations {
     /** Enter a symbol in given `scope` without potentially replacing the old copy. */
     def enterNoReplace(sym: Symbol, scope: MutableScope)(using Context): Unit =
       scope.enter(sym)
-      invalidateMemberCaches(sym)
+      invalidateMemberCachesFor(sym)
 
     /** Replace symbol `prev` (if defined in current class) by symbol `replacement`.
      *  If `prev` is not defined in current class, do nothing.
diff --git a/compiler/src/dotty/tools/dotc/typer/Namer.scala b/compiler/src/dotty/tools/dotc/typer/Namer.scala
index c40800862a31..a91882c099a1 100644
--- a/compiler/src/dotty/tools/dotc/typer/Namer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Namer.scala
@@ -1231,6 +1231,7 @@ class Namer { typer: Typer =>
       if (isDerivedValueClass(cls)) cls.setFlag(Final)
       cls.info = avoidPrivateLeaks(cls)
       cls.baseClasses.foreach(_.invalidateBaseTypeCache()) // we might have looked before and found nothing
+      cls.invalidateMemberCaches() // we might have checked for a member when parents were not known yet.
       cls.setNoInitsFlags(parentsKind(parents), untpd.bodyKind(rest))
       val ctorStable =
         if cls.is(Trait) then cls.is(NoInits)
diff --git a/tests/pos/i10634/AParser.scala b/tests/pos/i10634/AParser.scala
new file mode 100644
index 000000000000..c41b115d6454
--- /dev/null
+++ b/tests/pos/i10634/AParser.scala
@@ -0,0 +1,2 @@
+case class Parser(ctx: Context) extends BasicSupport
+
diff --git a/tests/pos/i10634/BasicSupport.scala b/tests/pos/i10634/BasicSupport.scala
new file mode 100644
index 000000000000..cf4ae7190ce4
--- /dev/null
+++ b/tests/pos/i10634/BasicSupport.scala
@@ -0,0 +1,10 @@
+// BasicSupport.scala
+trait BasicSupport:
+  self: Parser =>
+
+  object SymOps extends SymOps[ctx.type](ctx)
+  export SymOps._
+
+  def parse(sym: ctx.Symbol): Int =
+    sym.getVisibility()
+
diff --git a/tests/pos/i10634/Context.scala b/tests/pos/i10634/Context.scala
new file mode 100644
index 000000000000..0e22fd29d17d
--- /dev/null
+++ b/tests/pos/i10634/Context.scala
@@ -0,0 +1,8 @@
+// Context.scala
+trait Context:
+  type Symbol
+
+trait SymOps[C <: Context](val c: C):
+  extension (sym: c.Symbol)
+    def getVisibility(): Int = 0
+