diff --git a/cmd/drone-build/run.go b/cmd/drone-build/run.go
index dfd2cdb1..6c943040 100644
--- a/cmd/drone-build/run.go
+++ b/cmd/drone-build/run.go
@@ -32,6 +32,7 @@ func setup(c *Context) error {
 		Network:    false,
 		Privileged: false,
 		Volumes:    false,
+		Caching:    false,
 		Whitelist:  c.Plugins,
 	}
 
@@ -41,6 +42,14 @@ func setup(c *Context) error {
 		opts.Network = true
 		opts.Privileged = true
 		opts.Volumes = true
+		opts.Caching = true
+	}
+	// if repository is public, and a pull request, disable
+	// the cache.
+	if c.Repo.Private == false &&
+		c.Build.PullRequest != nil &&
+		c.Build.PullRequest.Number != 0 {
+		opts.Caching = false
 	}
 
 	// inject the matrix parameters into the yaml
diff --git a/pkg/yaml/parse.go b/pkg/yaml/parse.go
index 6b6b7658..c3735406 100644
--- a/pkg/yaml/parse.go
+++ b/pkg/yaml/parse.go
@@ -15,6 +15,7 @@ type Opts struct {
 	Volumes    bool
 	Network    bool
 	Privileged bool
+	Caching    bool
 	Whitelist  []string
 }
 
@@ -22,6 +23,7 @@ var DefaultOpts = &Opts{
 	Volumes:    false,
 	Network:    false,
 	Privileged: false,
+	Caching:    true,
 	Whitelist:  []string{"plugins/*"},
 }
 
@@ -86,6 +88,9 @@ func ParseSingle(raw string, opts *Opts, r *common.Repo) (*common.Config, error)
 		transform.RemovePrivileged(conf)
 	}
 	transform.Repo(conf, r)
+	if !opts.Caching {
+		transform.RemoveVolumes(conf)
+	}
 
 	// lint the yaml file
 	err = Lint(conf)