diff --git a/src/hydro/Default/hydro_iact.h b/src/hydro/Default/hydro_iact.h
index cf5bce5c69c625f0536837df3ce9bea7405a5444..d365c595f2bff9aad3754435377ea548af68313b 100644
--- a/src/hydro/Default/hydro_iact.h
+++ b/src/hydro/Default/hydro_iact.h
@@ -20,7 +20,7 @@
 #ifndef SWIFT_RUNNER_IACT_H
 #define SWIFT_RUNNER_IACT_H
 
-#include "gamma.h"
+#include "adiabatic_index.h"
 
 /**
  * @brief SPH interaction functions following the Gadget-2 version of SPH.
diff --git a/src/hydro/Minimal/hydro_iact.h b/src/hydro/Minimal/hydro_iact.h
index dd22aebd7d7f03080c50b079c4ffa87a5ae0ab7d..ae0da10534bb09440be64537b02bb280bf6a03bf 100644
--- a/src/hydro/Minimal/hydro_iact.h
+++ b/src/hydro/Minimal/hydro_iact.h
@@ -19,7 +19,7 @@
 #ifndef SWIFT_RUNNER_IACT_MINIMAL_H
 #define SWIFT_RUNNER_IACT_MINIMAL_H
 
-#include "gamma.h"
+#include "adiabatic_index.h"
 
 /**
  * @brief Minimal conservative implementation of SPH