diff --git a/src/parallel_io.c b/src/parallel_io.c
index 489b2fd9207d44e5ee157d046008631edd12aca8..7ba28d6f506338ea4e9a34343203bae4e794637d 100644
--- a/src/parallel_io.c
+++ b/src/parallel_io.c
@@ -441,7 +441,8 @@ void prepareArray(struct engine* e, hid_t grp, char* fileName, FILE* xmfFile,
   io_write_attribute_s(h_data, "Expression for physical CGS units", buffer);
 
   /* Write the actual number this conversion factor corresponds to */
-  const float factor = units_cgs_conversion_factor(snapshot_units, props.units);
+  const double factor =
+      units_cgs_conversion_factor(snapshot_units, props.units);
   io_write_attribute_d(
       h_data,
       "Conversion factor to CGS (not including cosmological corrections)",
diff --git a/src/serial_io.c b/src/serial_io.c
index 8f2c011061cd9b2ce9b828c83f8d451ddb804f10..9ea2b0f07fca332ba7b374afbb1a42693185d58a 100644
--- a/src/serial_io.c
+++ b/src/serial_io.c
@@ -326,7 +326,8 @@ void prepareArray(const struct engine* e, hid_t grp, char* fileName,
   io_write_attribute_s(h_data, "Expression for physical CGS units", buffer);
 
   /* Write the actual number this conversion factor corresponds to */
-  const float factor = units_cgs_conversion_factor(snapshot_units, props.units);
+  const double factor =
+      units_cgs_conversion_factor(snapshot_units, props.units);
   io_write_attribute_d(
       h_data,
       "Conversion factor to CGS (not including cosmological corrections)",
diff --git a/src/single_io.c b/src/single_io.c
index 54761878887d5cf1d8173a188fed3a0ba72f9297..afce1e1e6ebb6a8101ccfa109efd8df9e10fbd33 100644
--- a/src/single_io.c
+++ b/src/single_io.c
@@ -338,7 +338,8 @@ void writeArray(const struct engine* e, hid_t grp, char* fileName,
   io_write_attribute_s(h_data, "Expression for physical CGS units", buffer);
 
   /* Write the actual number this conversion factor corresponds to */
-  const float factor = units_cgs_conversion_factor(snapshot_units, props.units);
+  const double factor =
+      units_cgs_conversion_factor(snapshot_units, props.units);
   io_write_attribute_d(
       h_data,
       "Conversion factor to CGS (not including cosmological corrections)",