diff --git a/Dockerfile b/Dockerfile
index 1a3abf7..4a36135 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,6 +1,8 @@
 FROM golang:1.16-alpine as builder
 WORKDIR /build
 COPY . .
+# Make sure tests pass before building :)
+RUN CGO_ENABLED=0 go test ./...
 RUN CGO_ENABLED=0 go build -a -o render-drawio ./cmd/render-drawio
 
 FROM rlespinasse/drawio-desktop-headless:1.0.1
diff --git a/pkg/render/render.go b/pkg/render/render.go
index cc42ab7..50ef8f1 100644
--- a/pkg/render/render.go
+++ b/pkg/render/render.go
@@ -257,6 +257,13 @@ func GitHubActionSetFilesOutput(key, rootDir string, files []string) error {
 		}
 	}
 	// Run the generic function
-	GitHubActionSetOutput(key, strings.Join(files, " "))
+	GitHubActionSetOutput(key, joinQuotedStrings(files))
 	return nil
 }
+
+func joinQuotedStrings(strs []string) string {
+	for i := range strs {
+		strs[i] = fmt.Sprintf("%q", strs[i])
+	}
+	return strings.Join(strs, " ")
+}
diff --git a/pkg/render/render_test.go b/pkg/render/render_test.go
new file mode 100644
index 0000000..28653bf
--- /dev/null
+++ b/pkg/render/render_test.go
@@ -0,0 +1,24 @@
+package render
+
+import "testing"
+
+func Test_joinQuotedStrings(t *testing.T) {
+	tests := []struct {
+		name string
+		strs []string
+		want string
+	}{
+		{
+			name: "simple",
+			strs: []string{"foo bar", "bar baz"},
+			want: `"foo bar" "bar baz"`,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := joinQuotedStrings(tt.strs); got != tt.want {
+				t.Errorf("joinQuotedStrings() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}