diff --git a/src/core/ddsi/include/dds/ddsi/q_rtps.h b/src/core/ddsi/include/dds/ddsi/q_rtps.h
index dfe0d39..9359e5b 100644
--- a/src/core/ddsi/include/dds/ddsi/q_rtps.h
+++ b/src/core/ddsi/include/dds/ddsi/q_rtps.h
@@ -27,7 +27,7 @@ typedef int64_t seqno_t;
 
 #define PGUIDPREFIX(gp) (gp).u[0], (gp).u[1], (gp).u[2]
 #define PGUID(g) PGUIDPREFIX ((g).prefix), (g).entityid.u
-#define PGUIDFMT "%"PRIx32":%"PRIx32":%"PRIx32":%"PRIx32
+#define PGUIDFMT "%" PRIx32 ":%" PRIx32 ":%" PRIx32 ":%" PRIx32
 
 /* predefined entity ids; here viewed as an unsigned int, on the
    network as four bytes corresponding to the integer in network byte