diff --git a/Source/driver/Castro_advance_ctu.cpp b/Source/driver/Castro_advance_ctu.cpp
index 7659f445a2..01d2e7a1d3 100644
--- a/Source/driver/Castro_advance_ctu.cpp
+++ b/Source/driver/Castro_advance_ctu.cpp
@@ -31,19 +31,6 @@ Castro::do_advance_ctu (Real time, Real dt)
 
     MultiFab& S_new = get_new_data(State_Type);
 
-    MultiFab& old_source = get_old_data(Source_Type);
-    MultiFab& new_source = get_new_data(Source_Type);
-
-#ifdef MHD
-    MultiFab& Bx_old = get_old_data(Mag_Type_x);
-    MultiFab& By_old = get_old_data(Mag_Type_y);
-    MultiFab& Bz_old = get_old_data(Mag_Type_z);
-
-    MultiFab& Bx_new = get_new_data(Mag_Type_x);
-    MultiFab& By_new = get_new_data(Mag_Type_y);
-    MultiFab& Bz_new = get_new_data(Mag_Type_z);
-#endif 
-
     // Perform initialization steps.
 
     status = initialize_do_advance(time, dt);
@@ -77,11 +64,7 @@ Castro::do_advance_ctu (Real time, Real dt)
     construct_old_gravity(prev_time);
 #endif
 
-    do_old_sources(
-#ifdef MHD
-                   Bx_old, By_old, Bz_old,
-#endif                
-                   old_source, Sborder, S_new, prev_time, dt);
+    do_old_sources(prev_time, dt);
 
 #ifdef SIMPLIFIED_SDC
 #ifdef REACTIONS
@@ -116,11 +99,7 @@ Castro::do_advance_ctu (Real time, Real dt)
     construct_new_gravity(cur_time);
 #endif
 
-    do_new_sources(
-#ifdef MHD
-                    Bx_new, By_new, Bz_new,
-#endif  
-                    new_source, Sborder, S_new, cur_time, dt);
+    do_new_sources(cur_time, dt);
 
     // If the state has ghost zones, sync them up now since the hydro
     // source and new-time sources only work on the valid zones.
diff --git a/Source/sources/Castro_sources.H b/Source/sources/Castro_sources.H
index b4ac46288c..1e765bcb01 100644
--- a/Source/sources/Castro_sources.H
+++ b/Source/sources/Castro_sources.H
@@ -47,6 +47,16 @@
                         amrex::Real time, amrex::Real dt, bool apply_to_state = true);
 
 
+///
+/// Construct source terms at old time (convenience wrapper for CTU advance)
+///
+/// @param time     the current simulation time
+/// @param dt       the timestep to advance (e.g., go from time to
+///                    time + dt)
+///
+    void do_old_sources (amrex::Real time, amrex::Real dt);
+
+
 ///
 /// Construct the old-time source
 ///
@@ -83,6 +93,16 @@
                         amrex::Real time, amrex::Real dt, bool apply_to_state = true);
 
 
+///
+/// Construct new time sources (convenience wrapper for CTU advance)
+///
+/// @param time     the current simulation time
+/// @param dt       the timestep to advance (e.g., go from time to
+///                    time + dt)
+///
+    void do_new_sources (amrex::Real time, amrex::Real dt);
+
+
 ///
 /// Construct the new-time sources.
 ///
diff --git a/Source/sources/Castro_sources.cpp b/Source/sources/Castro_sources.cpp
index 86bc343d1e..bcdb1884b2 100644
--- a/Source/sources/Castro_sources.cpp
+++ b/Source/sources/Castro_sources.cpp
@@ -172,7 +172,26 @@ Castro::do_old_sources(
         });
 #endif
     }
+}
+
+void
+Castro::do_old_sources (Real time, Real dt)
+{
+    MultiFab& S_new = get_new_data(State_Type);
+
+    MultiFab& old_source = get_old_data(Source_Type);
 
+#ifdef MHD
+    MultiFab& Bx_old = get_old_data(Mag_Type_x);
+    MultiFab& By_old = get_old_data(Mag_Type_y);
+    MultiFab& Bz_old = get_old_data(Mag_Type_z);
+#endif
+
+    do_old_sources(
+#ifdef MHD
+                   Bx_old, By_old, Bz_old,
+#endif
+                   old_source, Sborder, S_new, time, dt);
 }
 
 void
@@ -235,6 +254,26 @@ Castro::do_new_sources(
 
 }
 
+void
+Castro::do_new_sources (Real time, Real dt)
+{
+    MultiFab& S_new = get_new_data(State_Type);
+
+    MultiFab& new_source = get_new_data(Source_Type);
+
+#ifdef MHD
+    MultiFab& Bx_new = get_new_data(Mag_Type_x);
+    MultiFab& By_new = get_new_data(Mag_Type_y);
+    MultiFab& Bz_new = get_new_data(Mag_Type_z);
+#endif
+
+    do_new_sources(
+#ifdef MHD
+                   Bx_new, By_new, Bz_new,
+#endif
+                   new_source, Sborder, S_new, time, dt);
+}
+
 void
 Castro::construct_old_source(int src, MultiFab& source, MultiFab& state_in, Real time, Real dt)
 {