diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1203fafc36..26d901d23a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@
 #### Fixes
 
 * Your contribution here.
+* [#2019](https://github.com/ruby-grape/grape/pull/2018): Avoid coercing parameter with multiple types to an empty Array - [@stanhu](https://github.com/stanhu).
 
 ### 1.3.1 (2020/03/11)
 
diff --git a/lib/grape/validations/validators/coerce.rb b/lib/grape/validations/validators/coerce.rb
index 561ec1bcf2..02bbe6908f 100644
--- a/lib/grape/validations/validators/coerce.rb
+++ b/lib/grape/validations/validators/coerce.rb
@@ -67,11 +67,7 @@ def valid_type?(val)
       def coerce_value(val)
         # define default values for structures, the dry-types lib which is used
         # for coercion doesn't accept nil as a value, so it would fail
-        if val.nil?
-          return []      if type == Array || type.is_a?(Array)
-          return Set.new if type == Set
-          return {}      if type == Hash
-        end
+        return coerce_nil(val) if val.nil?
 
         converter.call(val)
 
@@ -80,6 +76,13 @@ def coerce_value(val)
         Types::InvalidValue.new
       end
 
+      def coerce_nil(val)
+        return []      if type == Array
+        return Set.new if type == Set
+        return {}      if type == Hash
+        return val
+      end
+
       # Type to which the parameter will be coerced.
       #
       # @return [Class]
diff --git a/spec/grape/validations/validators/coerce_spec.rb b/spec/grape/validations/validators/coerce_spec.rb
index dbf57c9d57..2cfaceea83 100644
--- a/spec/grape/validations/validators/coerce_spec.rb
+++ b/spec/grape/validations/validators/coerce_spec.rb
@@ -180,6 +180,23 @@ def self.parsed?(value)
         expect(last_response.body).to eq(integer_class_name)
       end
 
+      it 'String' do
+        subject.params do
+          requires :string, coerce: String
+        end
+        subject.get '/string' do
+          params[:string].class
+        end
+
+        get '/string', string: 45
+        expect(last_response.status).to eq(200)
+        expect(last_response.body).to eq('String')
+
+        get '/string', string: nil
+        expect(last_response.status).to eq(200)
+        expect(last_response.body).to eq('NilClass')
+      end
+
       it 'is a custom type' do
         subject.params do
           requires :uri, coerce: SecureURIOnly
@@ -647,6 +664,19 @@ def self.parsed?(value)
         expect(last_response.body).to eq('String')
       end
 
+      it 'respects nil values' do
+        subject.params do
+          optional :a, types: [File, String]
+        end
+        subject.get '/' do
+          params[:a].class.to_s
+        end
+
+        get '/', a: nil
+        expect(last_response.status).to eq(200)
+        expect(last_response.body).to eq('NilClass')
+      end
+
       it 'fails when no coercion is possible' do
         subject.params do
           requires :a, types: [Boolean, Integer]