diff --git a/server/cmd/lsp/args.go b/server/cmd/lsp/args.go
index 62eead6..0e17297 100644
--- a/server/cmd/lsp/args.go
+++ b/server/cmd/lsp/args.go
@@ -6,6 +6,7 @@ import (
 	"runtime/debug"
 	"time"
 
+	"github.com/pherrymason/c3-lsp/internal/c3c"
 	"github.com/pherrymason/c3-lsp/internal/lsp/server"
 	"github.com/pherrymason/c3-lsp/pkg/option"
 )
@@ -47,10 +48,11 @@ func cmdLineArguments() (server.ServerOpts, bool, bool) {
 	//log.Printf("---------------")
 
 	return server.ServerOpts{
-		C3: server.C3Opts{
-			Version:    option.None[string](),
-			Path:       c3cPathOpt,
-			StdlibPath: stdlibPathOpt,
+		C3: c3c.C3Opts{
+			Version:     option.None[string](),
+			Path:        c3cPathOpt,
+			StdlibPath:  stdlibPathOpt,
+			CompileArgs: []string{},
 		},
 		Diagnostics: server.DiagnosticsOpts{
 			Delay:   time.Duration(*diagnosticsDelay),
diff --git a/server/internal/c3c/c3c.go b/server/internal/c3c/c3c.go
index 3250adc..c5d70ff 100644
--- a/server/internal/c3c/c3c.go
+++ b/server/internal/c3c/c3c.go
@@ -45,9 +45,16 @@ func GetC3Version(c3Path option.Option[string]) option.Option[string] {
 	return option.None[string]()
 }
 
-func CheckC3ErrorsCommand(c3Path option.Option[string], projectPath string) (bytes.Buffer, bytes.Buffer, error) {
-	binary := binaryPath(c3Path)
-	command := exec.Command(binary, "build", "--test")
+func CheckC3ErrorsCommand(c3Options C3Opts, projectPath string) (bytes.Buffer, bytes.Buffer, error) {
+	binary := binaryPath(c3Options.Path)
+
+	args := []string{"build", "--test"}
+	if len(c3Options.CompileArgs) > 0 {
+		args = append(args, c3Options.CompileArgs...)
+	}
+	log.Printf("C3C arguments used:", args)
+
+	command := exec.Command(binary, args...)
 	command.Dir = projectPath
 
 	// set var to get the output
diff --git a/server/internal/c3c/options.go b/server/internal/c3c/options.go
new file mode 100644
index 0000000..510f205
--- /dev/null
+++ b/server/internal/c3c/options.go
@@ -0,0 +1,10 @@
+package c3c
+
+import "github.com/pherrymason/c3-lsp/pkg/option"
+
+type C3Opts struct {
+	Version     option.Option[string] `json:"version"`
+	Path        option.Option[string] `json:"path"`
+	StdlibPath  option.Option[string] `json:"stdlib-path"`
+	CompileArgs []string              `json:"compile-args"`
+}
diff --git a/server/internal/lsp/server/Diagnostics.go b/server/internal/lsp/server/Diagnostics.go
index c67c37a..ca92a82 100644
--- a/server/internal/lsp/server/Diagnostics.go
+++ b/server/internal/lsp/server/Diagnostics.go
@@ -19,7 +19,7 @@ func (s *Server) RunDiagnostics(state *project_state.ProjectState, notify glsp.N
 	}
 
 	runDiagnostics := func() {
-		out, stdErr, err := c3c.CheckC3ErrorsCommand(s.options.C3.Path, state.GetProjectRootURI())
+		out, stdErr, err := c3c.CheckC3ErrorsCommand(s.options.C3, state.GetProjectRootURI())
 		log.Println("output:", out.String())
 		log.Println("output:", stdErr.String())
 		if err == nil {
diff --git a/server/internal/lsp/server/config.go b/server/internal/lsp/server/config.go
index d95a8b6..a4caafe 100644
--- a/server/internal/lsp/server/config.go
+++ b/server/internal/lsp/server/config.go
@@ -11,12 +11,6 @@ import (
 	"github.com/pherrymason/c3-lsp/pkg/option"
 )
 
-type C3Opts struct {
-	Version    option.Option[string] `json:"version"`
-	Path       option.Option[string] `json:"path"`
-	StdlibPath option.Option[string] `json:"stdlib-path"`
-}
-
 type DiagnosticsOpts struct {
 	Enabled bool          `json:"enabled"`
 	Delay   time.Duration `json:"delay"`
@@ -24,7 +18,7 @@ type DiagnosticsOpts struct {
 
 // ServerOpts holds the options to create a new Server.
 type ServerOpts struct {
-	C3          C3Opts          `json:"C3Opts"`
+	C3          c3c.C3Opts      `json:"C3Opts"`
 	Diagnostics DiagnosticsOpts `json:"Diagnostics"`
 
 	LogFilepath      option.Option[string]
@@ -34,9 +28,10 @@ type ServerOpts struct {
 
 type ServerOptsJson struct {
 	C3 struct {
-		Version    *string `json:"version,omitempty"`
-		Path       *string `json:"path,omitempty"`
-		StdlibPath *string `json:"stdlib-path,omitempty"`
+		Version     *string  `json:"version,omitempty"`
+		Path        *string  `json:"path,omitempty"`
+		StdlibPath  *string  `json:"stdlib-path,omitempty"`
+		CompileArgs []string `json:"compile-args"`
 	}
 
 	Diagnostics struct {
@@ -78,11 +73,16 @@ func (s *Server) loadServerConfigurationForWorkspace(path string) {
 	if options.C3.Version != nil {
 		s.options.C3.Version = option.Some(*options.C3.Version)
 	}
+
 	if options.C3.Path != nil {
 		s.options.C3.Path = option.Some(*options.C3.Path)
 		// Get version from binary
 	}
 
+	if len(options.C3.CompileArgs) > 0 {
+		s.options.C3.CompileArgs = options.C3.CompileArgs
+	}
+
 	c3Version := c3c.GetC3Version(s.options.C3.Path)
 	if c3Version.IsSome() {
 		s.options.C3.Version = c3Version