diff --git a/CHANGELOG.md b/CHANGELOG.md
index 51470e6..04f9246 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Holiday definitions
 
+## 2.5.2
+
+* Fix `de` issue cause by undefined `year_ranges` behavior in syntax
+
 ## 2.5.1
 
 * Fix Federal Reserve Independence Day tests
diff --git a/SYNTAX.md b/SYNTAX.md
index 3a4388a..573b283 100644
--- a/SYNTAX.md
+++ b/SYNTAX.md
@@ -139,9 +139,12 @@ Holidays.on(Date.civil(2016, 7, 1), :jp)
 
 #### `after`
 
+
 The 'after' selector will only find a match if the supplied date takes place
 after or equal to the holiday.
 
+A single number *must* be supplied. An array of integers will result in an error.
+
 Example:
 
 ```yaml
diff --git a/de.yaml b/de.yaml
index 3b8f2c9..afa4827 100644
--- a/de.yaml
+++ b/de.yaml
@@ -111,7 +111,7 @@ months:
     regions: [de_hb, de_hh, de_ni, de_sh]
     mday: 31
     year_ranges:
-    - after: [2018]
+    - after: 2018
   11:
   - name: Allerheiligen
     regions: [de_bw, de_by, de_nw, de_rp, de_sl]
diff --git a/lib/validation/month_validator.rb b/lib/validation/month_validator.rb
index 505751a..ce548cd 100644
--- a/lib/validation/month_validator.rb
+++ b/lib/validation/month_validator.rb
@@ -12,10 +12,31 @@ def call(months)
 
           month_defs.each do |month_def|
             raise Errors::InvalidMonth.new("All months must have a name, received: #{months}") if month_def['name'].nil? || month_def['name'].empty?
+
             raise Errors::InvalidRegions.new("A month must contain at least one region, received: #{months}") if month_def['regions'].nil? || month_def['regions'].empty?
+
             month_def['regions'].each do |region|
               raise Errors::InvalidRegions.new("A month must contain at least one region, received: #{months}") if region.nil? || region.empty?
             end
+
+            if month_def.key?("year_ranges")
+              month_def["year_ranges"].each do |yr|
+                yr.each_pair do |k, v|
+                  raise Errors::InvalidMonth.new("The :year_ranges value only accepts the following: :before, :after, :limited, :between, received: #{months}") unless [:before, :after, :limited, :between].include?(k.to_sym)
+
+                  case k
+                  when "after"
+                    raise Errors::InvalidMonth.new("The year_ranges.after value must contain a single 'year' integer, ex. 2018, received: #{months}") unless v.is_a?(Integer)
+                  when "limited"
+                    raise Errors::InvalidMonth.new("The year_ranges.limited value must contain an array of 'year' integers, ex. [2018], received: #{months}") unless v.is_a?(Array)
+
+                    v.each do |j|
+                     raise Errors::InvalidMonth.new("The year_ranges.limited value must contain an array of 'year' integers, ex. [2018], received: #{months}") unless j.is_a?(Integer)
+                    end
+                  end
+                end
+              end
+            end
           end
         end
 
diff --git a/spec/validation/month_validator_spec.rb b/spec/validation/month_validator_spec.rb
index 53ff06c..1069b95 100644
--- a/spec/validation/month_validator_spec.rb
+++ b/spec/validation/month_validator_spec.rb
@@ -67,5 +67,33 @@
         expect(e.message).to eq("A month must contain at least one region, received: #{months}")
       }
     end
+
+    it 'returns error if year_ranges contains unknown subkey' do
+      months = { 1 => [{"name"=>"Test Holiday", "regions"=>["test"], "mday"=>1, "year_ranges" => [{"blah" => [2018]}] }] }
+      expect { subject.call(months) }.to raise_error(Definitions::Errors::InvalidMonth) { |e|
+        expect(e.message).to eq("The :year_ranges value only accepts the following: :before, :after, :limited, :between, received: #{months}")
+      }
+    end
+
+    it 'returns error if :after value is not a single integer' do
+      months = { 1 => [{"name"=>"Test Holiday", "regions"=>["test"], "mday"=>1, "year_ranges" => [{"after" => [2018]}] }] }
+      expect { subject.call(months) }.to raise_error(Definitions::Errors::InvalidMonth) { |e|
+        expect(e.message).to eq("The year_ranges.after value must contain a single 'year' integer, ex. 2018, received: #{months}")
+      }
+    end
+
+    it 'returns error if :limited value is not an array' do
+      months = { 1 => [{"name"=>"Test Holiday", "regions"=>["test"], "mday"=>1, "year_ranges" => [{"limited" => 2018}] }] }
+      expect { subject.call(months) }.to raise_error(Definitions::Errors::InvalidMonth) { |e|
+        expect(e.message).to eq("The year_ranges.limited value must contain an array of 'year' integers, ex. [2018], received: #{months}")
+      }
+    end
+
+    it 'returns error if :limited value is not an array of integers' do
+      months = { 1 => [{"name"=>"Test Holiday", "regions"=>["test"], "mday"=>1, "year_ranges" => [{"limited" => ["blah"]}] }] }
+      expect { subject.call(months) }.to raise_error(Definitions::Errors::InvalidMonth) { |e|
+        expect(e.message).to eq("The year_ranges.limited value must contain an array of 'year' integers, ex. [2018], received: #{months}")
+      }
+    end
   end
 end