diff --git a/doc/Doxyfile.in b/doc/Doxyfile.in
index 844a6fa68029af3c119d7c03e09e6dec957c5da4..a4a28480a09baf4ef0ef58a1bff3a537326e5f16 100644
--- a/doc/Doxyfile.in
+++ b/doc/Doxyfile.in
@@ -765,6 +765,7 @@ INPUT		       += @top_srcdir@/src/gravity/Default
 INPUT		       += @top_srcdir@/src/stars/Default
 INPUT		       += @top_srcdir@/src/riemann
 INPUT		       += @top_srcdir@/src/potential/point_mass
+INPUT		       += @top_srcdir@/src/equation_of_state/ideal_gas
 INPUT		       += @top_srcdir@/src/cooling/none
 INPUT		       += @top_srcdir@/src/chemistry/none