diff --git a/lib/pg_search/scope_options.rb b/lib/pg_search/scope_options.rb
index 6fe515dd..c7cb64ea 100644
--- a/lib/pg_search/scope_options.rb
+++ b/lib/pg_search/scope_options.rb
@@ -79,10 +79,15 @@ def increment_counter
     delegate :connection, :quoted_table_name, to: :model
 
     def subquery
-      model
-        .unscoped
-        .select("#{primary_key} AS pg_search_id")
-        .select("#{rank} AS rank")
+      query = model.unscoped
+
+      query = if composite_primary_key?
+        query.select(model.primary_key.map.with_index(1) { |part, index| "#{quoted_column_name(part)} AS pg_search_id_#{index}" })
+      else
+        query.select("#{primary_key} AS pg_search_id")
+      end
+
+      query.select("#{rank} AS rank")
         .joins(subquery_join)
         .where(conditions)
         .limit(nil)
@@ -122,7 +127,11 @@ def order_within_rank
     end
 
     def primary_key
-      "#{quoted_table_name}.#{connection.quote_column_name(model.primary_key)}"
+      if composite_primary_key?
+        model.primary_key.map { |part| quoted_column_name(part) }.join(",")
+      else
+        quoted_column_name(model.primary_key)
+      end
     end
 
     def subquery_join
@@ -163,7 +172,14 @@ def rank
     end
 
     def rank_join(rank_table_alias)
-      "INNER JOIN (#{subquery.to_sql}) AS #{rank_table_alias} ON #{primary_key} = #{rank_table_alias}.pg_search_id"
+      join_condition = if composite_primary_key?
+        model.primary_key.map.with_index(1) { |part, index| "#{quoted_column_name(part)} = #{rank_table_alias}.pg_search_id_#{index}" }
+          .join(" AND ")
+      else
+        "#{primary_key} = #{rank_table_alias}.pg_search_id"
+      end
+
+      "INNER JOIN (#{subquery.to_sql}) AS #{rank_table_alias} ON #{join_condition}"
     end
 
     def include_table_aliasing_for_rank(scope)
@@ -173,5 +189,13 @@ def include_table_aliasing_for_rank(scope)
         new_scope.instance_eval { extend PgSearchRankTableAliasing }
       end
     end
+
+    def composite_primary_key?
+      model.primary_key.is_a?(Array)
+    end
+
+    def quoted_column_name(column)
+      "#{quoted_table_name}.#{connection.quote_column_name(column)}"
+    end
   end
 end
diff --git a/spec/integration/composite_primary_key_spec.rb b/spec/integration/composite_primary_key_spec.rb
new file mode 100644
index 00000000..a5e86af7
--- /dev/null
+++ b/spec/integration/composite_primary_key_spec.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+describe "composite_primary_key" do
+  context "without associations" do
+    with_model :Parent do
+      table primary_key: [:first_name, :last_name] do |t|
+        t.string :first_name
+        t.string :last_name
+        t.string :hobby
+      end
+
+      model do
+        include PgSearch::Model
+        self.primary_key = [:first_name, :last_name]
+        pg_search_scope :search_hobby, against: :hobby
+      end
+    end
+
+    before { Parent.create!(id: ["first_name", "last_name"], hobby: "golf") }
+    let!(:record_1) { Parent.create!(id: ["first_name_2", "last_name_2"], hobby: "basketball") }
+
+    it "searches without any issues" do
+      expect(Parent.search_hobby("basketball")).to eq([record_1])
+    end
+  end
+
+  context "searching against association with a composite_primary_key" do
+    with_model :Parent do
+      table primary_key: [:first_name, :last_name] do |t|
+        t.string :first_name
+        t.string :last_name
+        t.string :hobby
+      end
+
+      model do
+        include PgSearch::Model
+        has_many :children
+        self.primary_key = [:first_name, :last_name]
+      end
+    end
+
+    with_model :Child do
+      table do |t|
+        t.string :parent_first_name
+        t.string :parent_last_name
+      end
+
+      model do
+        include PgSearch::Model
+        belongs_to :parent, foreign_key: [:parent_first_name, :parent_last_name]
+
+        pg_search_scope :search_parent_hobby, associated_against: {
+          parent: [:hobby]
+        }
+      end
+    end
+
+    before do
+      parent = Parent.create!(id: ["first_name", "last_name"], hobby: "golf")
+      Child.create!(parent: parent)
+    end
+
+    let!(:record_1) do
+      parent = Parent.create!(id: ["first_name_2", "last_name_2"], hobby: "basketball")
+      Child.create!(parent: parent)
+    end
+
+    it "searches without any issues" do
+      expect(Child.search_parent_hobby("basketball")).to eq([record_1])
+    end
+  end
+end