diff --git a/src/Perl6/Metamodel/AttributeContainer.nqp b/src/Perl6/Metamodel/AttributeContainer.nqp
index b87e650a25f..8205517e44d 100644
--- a/src/Perl6/Metamodel/AttributeContainer.nqp
+++ b/src/Perl6/Metamodel/AttributeContainer.nqp
@@ -25,6 +25,7 @@ role Perl6::Metamodel::AttributeContainer {
     method compose_attributes($obj, :$compiler_services) {
         my %seen_with_accessor;
         my %meths := self.method_table($obj);
+        %meths := %meths.FLATTENABLE_HASH() unless nqp::ishash(%meths);
         my %orig_meths;
         for %meths {
             %orig_meths{$_.key} := 1;
diff --git a/src/Perl6/Metamodel/MROBasedMethodDispatch.nqp b/src/Perl6/Metamodel/MROBasedMethodDispatch.nqp
index 48d35825c03..c849bb8f886 100644
--- a/src/Perl6/Metamodel/MROBasedMethodDispatch.nqp
+++ b/src/Perl6/Metamodel/MROBasedMethodDispatch.nqp
@@ -63,8 +63,9 @@ role Perl6::Metamodel::MROBasedMethodDispatch {
             @mro_reversed.unshift($_);
         }
         for @mro_reversed {
-            for $_.HOW.method_table($_) {
-                %cache{$_.key} := $_.value;
+            my $method_table := $_.HOW.method_table($_);
+            for nqp::ishash($method_table) ?? $method_table !! $method_table.FLATTENABLE_HASH() {
+                %cache{$_.key} := nqp::decont($_.value);
             }
             if nqp::can($_.HOW, 'is_composed') && !$_.HOW.is_composed($_) {
                 $authable := 0;
@@ -72,7 +73,8 @@ role Perl6::Metamodel::MROBasedMethodDispatch {
         }
 
         # Also add submethods.
-        for $obj.HOW.submethod_table($obj) {
+        my $submethod_table := $obj.HOW.submethod_table($obj);
+        for nqp::ishash($submethod_table) ?? $submethod_table !! $submethod_table.FLATTENABLE_HASH() {
             %cache{$_.key} := $_.value;
         }
 
diff --git a/src/Perl6/Metamodel/MethodContainer.nqp b/src/Perl6/Metamodel/MethodContainer.nqp
index b5c2a46d1e9..d67d2181e5a 100644
--- a/src/Perl6/Metamodel/MethodContainer.nqp
+++ b/src/Perl6/Metamodel/MethodContainer.nqp
@@ -52,11 +52,13 @@ role Perl6::Metamodel::MethodContainer {
         # If local flag was not passed, include those from parents.
         unless $local {
             for self.parents($obj, :all($all), :excl($excl)) {
-                for $_.HOW.method_table($_) {
-                    @meths.push(nqp::hllizefor($_.value, 'perl6'));
+                my %method_table := $_.HOW.method_table($_);
+                for nqp::ishash(%method_table) ?? %method_table !! %method_table.FLATTENABLE_HASH {
+                    @meths.push(nqp::hllizefor(nqp::decont($_.value), 'perl6'));
                 }
-                for $_.HOW.submethod_table($_) {
-                    @meths.push(nqp::hllizefor($_.value, 'perl6'));
+                my %submethod_table := $_.HOW.submethod_table($_);
+                for nqp::ishash(%submethod_table) ?? %submethod_table !! %submethod_table.FLATTENABLE_HASH {
+                    @meths.push(nqp::hllizefor(nqp::decont($_.value), 'perl6'));
                 }
             }
         }
@@ -86,13 +88,15 @@ role Perl6::Metamodel::MethodContainer {
     method lookup($obj, $name) {
         for self.mro($obj) {
             my %meth := $_.HOW.method_table($obj);
+            %meth := %meth.FLATTENABLE_HASH unless nqp::ishash(%meth);
             if nqp::existskey(%meth, $name) {
-                return %meth{$name};
+                return nqp::decont(%meth{$name});
             }
             if nqp::can($_.HOW, 'submethod_table') {
                 my %submeth := $_.HOW.submethod_table($obj);
+                %submeth := %submeth.FLATTENABLE_HASH unless nqp::ishash(%submeth);
                 if nqp::existskey(%submeth, $name) {
-                    return %submeth{$name};
+                    return nqp::decont(%submeth{$name});
                 }
             }
         }