diff --git a/lib/tapioca/dsl/compilers/active_record_relations.rb b/lib/tapioca/dsl/compilers/active_record_relations.rb
index 3c536f518..bed31c4f7 100644
--- a/lib/tapioca/dsl/compilers/active_record_relations.rb
+++ b/lib/tapioca/dsl/compilers/active_record_relations.rb
@@ -372,7 +372,12 @@ def create_group_chain_methods(klass)
             return_type: "T.self_type",
           )
 
-          (CALCULATION_METHODS + [:size]).each do |method_name|
+          klass.create_method(
+            "size",
+            return_type: "Integer",
+          )
+
+          CALCULATION_METHODS.each do |method_name|
             case method_name
             when :average, :maximum, :minimum
               klass.create_method(
@@ -400,9 +405,9 @@ def create_group_chain_methods(klass)
                 ],
                 return_type: "T::Hash[T.untyped, Integer]",
               )
-            when :sum, :size
+            when :sum
               klass.create_method(
-                method_name.to_s,
+                "sum",
                 parameters: [
                   create_opt_param("column_name", type: "T.nilable(T.any(String, Symbol))", default: "nil"),
                   create_block_param("block", type: "T.nilable(T.proc.params(record: T.untyped).returns(T.untyped))"),
diff --git a/spec/tapioca/dsl/compilers/active_record_relations_spec.rb b/spec/tapioca/dsl/compilers/active_record_relations_spec.rb
index f15e8fce1..40b228fdc 100644
--- a/spec/tapioca/dsl/compilers/active_record_relations_spec.rb
+++ b/spec/tapioca/dsl/compilers/active_record_relations_spec.rb
@@ -660,8 +660,8 @@ def maximum(column_name); end
                     sig { params(column_name: T.any(String, Symbol)).returns(T::Hash[T.untyped, T.untyped]) }
                     def minimum(column_name); end
 
-                    sig { params(column_name: T.nilable(T.any(String, Symbol)), block: T.nilable(T.proc.params(record: T.untyped).returns(T.untyped))).returns(T::Hash[T.untyped, T.any(Integer, Float, BigDecimal)]) }
-                    def size(column_name = nil, &block); end
+                    sig { returns(Integer) }
+                    def size; end
 
                     sig { params(column_name: T.nilable(T.any(String, Symbol)), block: T.nilable(T.proc.params(record: T.untyped).returns(T.untyped))).returns(T::Hash[T.untyped, T.any(Integer, Float, BigDecimal)]) }
                     def sum(column_name = nil, &block); end
@@ -765,8 +765,8 @@ def maximum(column_name); end
                     sig { params(column_name: T.any(String, Symbol)).returns(T::Hash[T.untyped, T.untyped]) }
                     def minimum(column_name); end
 
-                    sig { params(column_name: T.nilable(T.any(String, Symbol)), block: T.nilable(T.proc.params(record: T.untyped).returns(T.untyped))).returns(T::Hash[T.untyped, T.any(Integer, Float, BigDecimal)]) }
-                    def size(column_name = nil, &block); end
+                    sig { returns(Integer) }
+                    def size; end
 
                     sig { params(column_name: T.nilable(T.any(String, Symbol)), block: T.nilable(T.proc.params(record: T.untyped).returns(T.untyped))).returns(T::Hash[T.untyped, T.any(Integer, Float, BigDecimal)]) }
                     def sum(column_name = nil, &block); end
@@ -1386,8 +1386,8 @@ def maximum(column_name); end
                     sig { params(column_name: T.any(String, Symbol)).returns(T::Hash[T.untyped, T.untyped]) }
                     def minimum(column_name); end
 
-                    sig { params(column_name: T.nilable(T.any(String, Symbol)), block: T.nilable(T.proc.params(record: T.untyped).returns(T.untyped))).returns(T::Hash[T.untyped, T.any(Integer, Float, BigDecimal)]) }
-                    def size(column_name = nil, &block); end
+                    sig { returns(Integer) }
+                    def size; end
 
                     sig { params(column_name: T.nilable(T.any(String, Symbol)), block: T.nilable(T.proc.params(record: T.untyped).returns(T.untyped))).returns(T::Hash[T.untyped, T.any(Integer, Float, BigDecimal)]) }
                     def sum(column_name = nil, &block); end
@@ -1491,8 +1491,8 @@ def maximum(column_name); end
                     sig { params(column_name: T.any(String, Symbol)).returns(T::Hash[T.untyped, T.untyped]) }
                     def minimum(column_name); end
 
-                    sig { params(column_name: T.nilable(T.any(String, Symbol)), block: T.nilable(T.proc.params(record: T.untyped).returns(T.untyped))).returns(T::Hash[T.untyped, T.any(Integer, Float, BigDecimal)]) }
-                    def size(column_name = nil, &block); end
+                    sig { returns(Integer) }
+                    def size; end
 
                     sig { params(column_name: T.nilable(T.any(String, Symbol)), block: T.nilable(T.proc.params(record: T.untyped).returns(T.untyped))).returns(T::Hash[T.untyped, T.any(Integer, Float, BigDecimal)]) }
                     def sum(column_name = nil, &block); end