diff --git a/src/activity_handlers.cpp b/src/activity_handlers.cpp
index b44978b21e92..7cb3c474fb0c 100644
--- a/src/activity_handlers.cpp
+++ b/src/activity_handlers.cpp
@@ -246,9 +246,9 @@ static const quality_id qual_LOCKPICK( "LOCKPICK" );
 static const species_id HUMAN( "HUMAN" );
 static const species_id ZOMBIE( "ZOMBIE" );
 
-static const std::string trait_flag_CANNIBAL( "CANNIBAL" );
-static const std::string trait_flag_PSYCHOPATH( "PSYCHOPATH" );
-static const std::string trait_flag_SAPIOVORE( "SAPIOVORE" );
+static const trait_flag_str_id trait_flag_CANNIBAL( "CANNIBAL" );
+static const trait_flag_str_id trait_flag_PSYCHOPATH( "PSYCHOPATH" );
+static const trait_flag_str_id trait_flag_SAPIOVORE( "SAPIOVORE" );
 
 static const bionic_id bio_ears( "bio_ears" );
 static const bionic_id bio_painkiller( "bio_painkiller" );
diff --git a/src/character.cpp b/src/character.cpp
index cb2dec4555c6..9e950664411d 100644
--- a/src/character.cpp
+++ b/src/character.cpp
@@ -3445,16 +3445,16 @@ void Character::practice( const skill_id &id, int amount, int cap, bool suppress
             amount = 0;
         }
     }
-    if( has_trait_flag( "PRED2" ) && skill.is_combat_skill() ) {
+    if( has_trait_flag( trait_flag_str_id( "PRED2" ) ) && skill.is_combat_skill() ) {
         if( one_in( 3 ) ) {
             amount *= 2;
         }
     }
-    if( has_trait_flag( "PRED3" ) && skill.is_combat_skill() ) {
+    if( has_trait_flag( trait_flag_str_id( "PRED3" ) ) && skill.is_combat_skill() ) {
         amount *= 2;
     }
 
-    if( has_trait_flag( "PRED4" ) && skill.is_combat_skill() ) {
+    if( has_trait_flag( trait_flag_str_id( "PRED4" ) ) && skill.is_combat_skill() ) {
         amount *= 3;
     }
 
@@ -3488,7 +3488,7 @@ void Character::practice( const skill_id &id, int amount, int cap, bool suppress
         focus_pool -= chance_to_drop / 100;
         // Apex Predators don't think about much other than killing.
         // They don't lose Focus when practicing combat skills.
-        if( ( rng( 1, 100 ) <= ( chance_to_drop % 100 ) ) && ( !( has_trait_flag( "PRED4" ) &&
+        if( ( rng( 1, 100 ) <= ( chance_to_drop % 100 ) ) && ( !( has_trait_flag( trait_flag_str_id( "PRED4" ) ) &&
                 skill.is_combat_skill() ) ) ) {
             focus_pool--;
         }
@@ -3599,17 +3599,14 @@ void Character::apply_skill_boost()
 void Character::do_skill_rust()
 {
     const int rust_rate_tmp = rust_rate();
-    static const std::string PRED2( "PRED2" );
-    static const std::string PRED3( "PRED3" );
-    static const std::string PRED4( "PRED4" );
     for( std::pair<const skill_id, SkillLevel> &pair : *_skills ) {
         const Skill &aSkill = *pair.first;
         SkillLevel &skill_level_obj = pair.second;
 
         if( aSkill.is_combat_skill() &&
-            ( ( has_trait_flag( PRED2 ) && calendar::once_every( 8_hours ) ) ||
-              ( has_trait_flag( PRED3 ) && calendar::once_every( 4_hours ) ) ||
-              ( has_trait_flag( PRED4 ) && calendar::once_every( 3_hours ) ) ) ) {
+            ( ( has_trait_flag( trait_flag_str_id( "PRED2" ) ) && calendar::once_every( 8_hours ) ) ||
+              ( has_trait_flag( trait_flag_str_id( "PRED3" ) ) && calendar::once_every( 4_hours ) ) ||
+              ( has_trait_flag( trait_flag_str_id( "PRED4" ) ) && calendar::once_every( 3_hours ) ) ) ) {
             // Their brain is optimized to remember this
             if( one_in( 13 ) ) {
                 // They've already passed the roll to avoid rust at
@@ -4437,7 +4434,7 @@ std::pair<std::string, nc_color> Character::get_fatigue_description() const
 
 void Character::mod_thirst( int nthirst )
 {
-    if( has_trait_flag( "NO_THIRST" ) ) {
+    if( has_trait_flag( trait_flag_str_id( "NO_THIRST" ) ) ) {
         return;
     }
     set_thirst( std::max( -100, thirst + nthirst ) );
@@ -7077,7 +7074,7 @@ void Character::set_rad( int new_rad )
 
 void Character::mod_rad( int mod )
 {
-    if( has_trait_flag( "NO_RADIATION" ) ) {
+    if( has_trait_flag( trait_flag_str_id( "NO_RADIATION" ) ) ) {
         return;
     }
     set_rad( std::max( 0, get_rad() + mod ) );
diff --git a/src/character.h b/src/character.h
index c3ff9d3f7ebf..d48b461d6cab 100644
--- a/src/character.h
+++ b/src/character.h
@@ -703,7 +703,7 @@ class Character : public Creature, public visitable<Character>
         /** Returns true if the player has the entered starting trait */
         bool has_base_trait( const trait_id &b ) const;
         /** Returns true if player has a trait with a flag */
-        bool has_trait_flag( const std::string &b ) const;
+        bool has_trait_flag( const trait_flag_id &b ) const;
         /** Returns true if character has a trait which cancels the entered trait. */
         bool has_opposite_trait( const trait_id &flag ) const;
 
diff --git a/src/consumption.cpp b/src/consumption.cpp
index 344bdcda4f13..979e3ea7bb50 100644
--- a/src/consumption.cpp
+++ b/src/consumption.cpp
@@ -755,7 +755,7 @@ ret_val<edible_rating> Character::will_eat( const item &food, bool interactive )
     }
 
     const bool carnivore = has_trait( trait_CARNIVORE );
-    if( food.has_flag( flag_CANNIBALISM ) && !has_trait_flag( "CANNIBAL" ) ) {
+    if( food.has_flag( flag_CANNIBALISM ) && !has_trait_flag( trait_flag_str_id( "CANNIBAL" ) ) ) {
         add_consequence( _( "The thought of eating human flesh makes you feel sick." ),
                          edible_rating::cannibalism );
     }
diff --git a/src/item.cpp b/src/item.cpp
index 10f9c46324d1..a6e0f5dd46b8 100644
--- a/src/item.cpp
+++ b/src/item.cpp
@@ -156,7 +156,7 @@ static const quality_id qual_JACK( "JACK" );
 static const quality_id qual_LIFT( "LIFT" );
 static const species_id ROBOT( "ROBOT" );
 
-static const std::string trait_flag_CANNIBAL( "CANNIBAL" );
+static const trait_flag_str_id trait_flag_CANNIBAL( "CANNIBAL" );
 
 static const bionic_id bio_digestion( "bio_digestion" );
 
diff --git a/src/iuse_actor.cpp b/src/iuse_actor.cpp
index feba98829f30..4b2cde781009 100644
--- a/src/iuse_actor.cpp
+++ b/src/iuse_actor.cpp
@@ -2050,9 +2050,9 @@ int enzlave_actor::use( player &p, item &it, bool t, const tripoint & ) const
     int tolerance_level = 9;
     if( p.has_trait( trait_PSYCHOPATH ) || p.has_trait( trait_SAPIOVORE ) ) {
         tolerance_level = 0;
-    } else if( p.has_trait_flag( "PRED4" ) ) {
+    } else if( p.has_trait_flag( trait_flag_str_id( "PRED4" ) ) ) {
         tolerance_level = 5;
-    } else if( p.has_trait_flag( "PRED3" ) ) {
+    } else if( p.has_trait_flag( trait_flag_str_id( "PRED3" ) ) ) {
         tolerance_level = 7;
     }
 
@@ -2096,9 +2096,9 @@ int enzlave_actor::use( player &p, item &it, bool t, const tripoint & ) const
         if( p.has_trait( trait_PACIFIST ) ) {
             moraleMalus *= 5;
             maxMalus *= 3;
-        } else if( p.has_trait_flag( "PRED1" ) ) {
+        } else if( p.has_trait_flag( trait_flag_str_id( "PRED1" ) ) ) {
             moraleMalus /= 4;
-        } else if( p.has_trait_flag( "PRED2" ) ) {
+        } else if( p.has_trait_flag( trait_flag_str_id( "PRED2" ) ) ) {
             moraleMalus /= 5;
         }
 
diff --git a/src/magic.cpp b/src/magic.cpp
index 7815169c505f..df38dfec12ae 100644
--- a/src/magic.cpp
+++ b/src/magic.cpp
@@ -758,13 +758,13 @@ float spell::spell_fail( const Character &guy ) const
         return 1.0f;
     }
     float fail_chance = std::pow( ( effective_skill - 30.0f ) / 30.0f, 2 );
-    if( has_flag( spell_flag::SOMATIC ) && !guy.has_trait_flag( "SUBTLE_SPELL" ) ) {
+    if( has_flag( spell_flag::SOMATIC ) && !guy.has_trait_flag( trait_flag_str_id( "SUBTLE_SPELL" ) ) ) {
         // the first 20 points of encumbrance combined is ignored
         const int arms_encumb = std::max( 0, guy.encumb( bp_arm_l ) + guy.encumb( bp_arm_r ) - 20 );
         // each encumbrance point beyond the "gray" color counts as half an additional fail %
         fail_chance += arms_encumb / 200.0f;
     }
-    if( has_flag( spell_flag::VERBAL ) && !guy.has_trait_flag( "SILENT_SPELL" ) ) {
+    if( has_flag( spell_flag::VERBAL ) && !guy.has_trait_flag( trait_flag_str_id( "SILENT_SPELL" ) ) ) {
         // a little bit of mouth encumbrance is allowed, but not much
         const int mouth_encumb = std::max( 0, guy.encumb( bp_mouth ) - 5 );
         fail_chance += mouth_encumb / 100.0f;
diff --git a/src/mondeath.cpp b/src/mondeath.cpp
index 4b4ebc740618..68b63d44a691 100644
--- a/src/mondeath.cpp
+++ b/src/mondeath.cpp
@@ -438,8 +438,8 @@ void mdeath::guilt( monster &z )
     guilt_tresholds[50] = _( "You regret killing %s." );
     guilt_tresholds[25] = _( "You feel remorse for killing %s." );
 
-    if( g->u.has_trait( trait_PSYCHOPATH ) || g->u.has_trait_flag( "PRED3" ) ||
-        g->u.has_trait_flag( "PRED4" ) || g->u.has_trait( trait_KILLER ) ) {
+    if( g->u.has_trait( trait_PSYCHOPATH ) || g->u.has_trait_flag( trait_flag_str_id( "PRED3" ) ||
+        g->u.has_trait_flag( trait_flag_str_id( "PRED4" ) || g->u.has_trait( trait_KILLER ) ) {
         return;
     }
     if( rl_dist( z.pos(), g->u.pos() ) > MAX_GUILT_DISTANCE ) {
@@ -458,7 +458,7 @@ void mdeath::guilt( monster &z )
                                 "about their deaths anymore." ), z.name( maxKills ) );
         }
         return;
-    } else if( ( g->u.has_trait_flag( "PRED1" ) ) || ( g->u.has_trait_flag( "PRED2" ) ) ) {
+    } else if( ( g->u.has_trait_flag( trait_flag_str_id( "PRED1" ) ) || ( g->u.has_trait_flag( trait_flag_str_id( "PRED2" ) ) ) {
         msg = ( _( "Culling the weak is distasteful, but necessary." ) );
         msgtype = m_neutral;
     } else {
@@ -481,9 +481,9 @@ void mdeath::guilt( monster &z )
         moraleMalus /= 10;
         if( g->u.has_trait( trait_PACIFIST ) ) {
             moraleMalus *= 5;
-        } else if( g->u.has_trait_flag( "PRED1" ) ) {
+        } else if( g->u.has_trait_flag( trait_flag_str_id( "PRED1" ) ) {
             moraleMalus /= 4;
-        } else if( g->u.has_trait_flag( "PRED2" ) ) {
+        } else if( g->u.has_trait_flag( trait_flag_str_id( "PRED2" ) ) {
             moraleMalus /= 5;
         }
     }
diff --git a/src/mutation.cpp b/src/mutation.cpp
index 03a1f30198d7..38a86f0d5174 100644
--- a/src/mutation.cpp
+++ b/src/mutation.cpp
@@ -103,7 +103,7 @@ bool Character::has_trait( const trait_id &b ) const
     return my_mutations.count( b ) || enchantment_cache->get_mutations().count( b );
 }
 
-bool Character::has_trait_flag( const std::string &b ) const
+bool Character::has_trait_flag( const trait_flag_id &b ) const
 {
     for( const mutation_branch *mut : cached_mutations ) {
         if( mut->flags.count( b ) > 0 ) {