diff --git a/core/src/kernel/magic.c b/core/src/kernel/magic.c
index d59113ba0..95b5ec0ff 100644
--- a/core/src/kernel/magic.c
+++ b/core/src/kernel/magic.c
@@ -2048,11 +2048,11 @@ static spellparameter *add_spellparameter(region * target_r, unit * u,
   return par;
 }
 
-struct unit * co_get_caster(struct castorder * co) {
+struct unit * co_get_caster(const struct castorder * co) {
   return co->_familiar ? co->_familiar : co->magician.u;
 }
 
-struct region * co_get_region(struct castorder * co) {
+struct region * co_get_region(const struct castorder * co) {
   return co->_rtarget;
 }
 
diff --git a/core/src/kernel/magic.h b/core/src/kernel/magic.h
index eb3c27d4c..00a752cf3 100644
--- a/core/src/kernel/magic.h
+++ b/core/src/kernel/magic.h
@@ -135,8 +135,8 @@ typedef struct sc_mage {
     struct spellparameter *par; /* für weitere Parameter */
   } castorder;
 
-  struct unit * co_get_caster(struct castorder * co);
-  struct region * co_get_region(struct castorder * co);
+  struct unit * co_get_caster(const struct castorder * co);
+  struct region * co_get_region(const struct castorder * co);
 
   typedef struct spell_component {
     const struct resource_type *type;
diff --git a/core/src/kernel/spell.h b/core/src/kernel/spell.h
index 53be0b6cc..40404b4d2 100644
--- a/core/src/kernel/spell.h
+++ b/core/src/kernel/spell.h
@@ -24,7 +24,7 @@ extern "C" {
 
   struct castorder;
   typedef int (*spell_f)(struct castorder * co);
-  typedef void(*fumble_f)(struct castorder * co);
+  typedef void(*fumble_f)(const struct castorder * co);
 
   typedef struct spell {
     unsigned int id;
diff --git a/src/spells/spells.c b/src/spells/spells.c
index 234edee51..e595000ff 100644
--- a/src/spells/spells.c
+++ b/src/spells/spells.c
@@ -1167,7 +1167,7 @@ static int sp_mallornhain(castorder * co)
   return cast_level;
 }
 
-void patzer_ents(castorder * co)
+static void fumble_ents(const castorder * co)
 {
   int ents;
   unit *u;
@@ -2301,7 +2301,7 @@ static int sp_earthquake(castorder * co)
 /* ------------------------------------------------------------- */
 /* CHAOS / M_DRAIG / Draig */
 /* ------------------------------------------------------------- */
-void patzer_peasantmob(castorder * co)
+void patzer_peasantmob(const castorder * co)
 {
   int anteil = 6, n;
   unit *u;
@@ -2488,7 +2488,7 @@ static int sp_fumblecurse(castorder * co)
   return cast_level;
 }
 
-void patzer_fumblecurse(castorder * co)
+void patzer_fumblecurse(const castorder * co)
 {
   unit *mage = co->magician.u;
   int cast_level = co->level;
@@ -6469,13 +6469,13 @@ static spelldata spell_functions[] = {
   /* M_GWYRRD */
   { "stonegolem", sp_create_stonegolem, 0},
   { "irongolem", sp_create_irongolem, 0},
-  { "treegrow", sp_hain, patzer_ents},
+  { "treegrow", sp_hain, fumble_ents},
   { "rustweapon", sp_rosthauch, 0},
   { "cold_protection", sp_kaelteschutz, 0},
   { "ironkeeper", sp_ironkeeper, 0},
   { "magicstreet", sp_magicstreet, 0},
   { "windshield", sp_windshield, 0},
-  { "mallorntreegrow", sp_mallornhain, patzer_ents},
+  { "mallorntreegrow", sp_mallornhain, fumble_ents},
   { "goodwinds", sp_goodwinds, 0},
   { "healing", sp_healing, 0},
   { "reelingarrows", sp_reeling_arrows, 0},