diff --git a/src/parallel_io.c b/src/parallel_io.c
index 0b66a4314ce8f883b9ac9110141a72131be32226..20b12bdd9aa6f8c12ca6140ab5642dcc12119890 100644
--- a/src/parallel_io.c
+++ b/src/parallel_io.c
@@ -701,7 +701,7 @@ void write_output_parallel(struct engine* e, const char* baseName,
   writeUnitSystem(h_file, snapshot_units, "Units");
 
   /* Print the system of Units used internally */
-  writeUnitSystem(h_file, internal_units, "InternalUnits");
+  writeUnitSystem(h_file, internal_units, "InternalCodeUnits");
 
   /* Loop over all particle types */
   for (int ptype = 0; ptype < NUM_PARTICLE_TYPES; ptype++) {
diff --git a/src/serial_io.c b/src/serial_io.c
index c023303241f9b1c21c13cfcb43a25e8923e0036e..704d34ad672306130a73fd01687c44db16a15f97 100644
--- a/src/serial_io.c
+++ b/src/serial_io.c
@@ -759,7 +759,7 @@ void write_output_serial(struct engine* e, const char* baseName,
     writeUnitSystem(h_file, snapshot_units, "Units");
 
     /* Print the system of Units used internally */
-    writeUnitSystem(h_file, internal_units, "InternalUnits");
+    writeUnitSystem(h_file, internal_units, "InternalCodeUnits");
 
     /* Loop over all particle types */
     for (int ptype = 0; ptype < NUM_PARTICLE_TYPES; ptype++) {
diff --git a/src/single_io.c b/src/single_io.c
index 50fe44d7515c8df7380c3510620550cb2adc8f60..9bb99411028aaabf7c083b968acac63133f660a3 100644
--- a/src/single_io.c
+++ b/src/single_io.c
@@ -605,7 +605,7 @@ void write_output_single(struct engine* e, const char* baseName,
   writeUnitSystem(h_file, snapshot_units, "Units");
 
   /* Print the system of Units used internally */
-  writeUnitSystem(h_file, internal_units, "InternalUnits");
+  writeUnitSystem(h_file, internal_units, "InternalCodeUnits");
 
   /* Loop over all particle types */
   for (int ptype = 0; ptype < NUM_PARTICLE_TYPES; ptype++) {