diff --git a/ostream.cpp b/ostream.cpp
index 5e6d5d3..c4ea5a7 100644
--- a/ostream.cpp
+++ b/ostream.cpp
@@ -132,8 +132,8 @@ operator<< (std::ostream &os, const VkPhysicalDeviceLimits &l)
 std::ostream&
 operator<< (std::ostream &os, const VkPhysicalDeviceProperties &p)
 {
-    os << "{ api: ";    write_version (os, p.apiVersion);
-    os << ", driver: "; write_version (os, p.driverVersion);
+    os << "{ api: '";    write_version (os, p.apiVersion) << "'";
+    os << ", driver: '"; write_version (os, p.driverVersion) << "'";
     os << ", vendor: 0x" << std::hex << std::setw (4) << std::setfill ('0') << p.vendorID << std::dec;
     os << ", device: 0x" << std::hex << std::setw (4) << std::setfill ('0') << p.deviceID << std::dec;
     os << ", name: '"  << p.deviceName << "'";