diff --git a/rubygem-webmock.spec b/rubygem-webmock.spec
index dae5ee1..a036ce1 100644
--- a/rubygem-webmock.spec
+++ b/rubygem-webmock.spec
@@ -63,6 +63,9 @@ Documentation for %{name}.
 %prep
 %setup -q -n %{gem_name}-%{version}
 
+# JSON is required by lib/webmock/request_body_diff.rb
+%gemspec_add_dep -g json
+
 %patch0 -p1
 
 %build