diff --git a/data/json/npcs/TALK_TEST.json b/data/json/npcs/TALK_TEST.json
index 75779c4b9e256..c3ebc235753e6 100644
--- a/data/json/npcs/TALK_TEST.json
+++ b/data/json/npcs/TALK_TEST.json
@@ -1210,17 +1210,17 @@
       {
         "text": "Sets Test Proficiency learning done to 12 hours total.",
         "topic": "TALK_DONE",
-        "effect": { "math": [ "u_proficiency('prof_test', 'format': 'time_spent', 'direct': 'true')", "=", "time('12h')" ] }
+        "effect": { "math": [ "u_proficiency('prof_test', 'format': 'time_spent', 'direct': true)", "=", "time('12h')" ] }
       },
       {
         "text": "Sets Test Proficiency learning done to -1.",
         "topic": "TALK_DONE",
-        "effect": { "math": [ "u_proficiency('prof_test', 'format': 'time_spent', 'direct': 'true')", "=", "-1" ] }
+        "effect": { "math": [ "u_proficiency('prof_test', 'format': 'time_spent', 'direct': true)", "=", "-1" ] }
       },
       {
         "text": "Sets Test Proficiency learning done to 24h.",
         "topic": "TALK_DONE",
-        "effect": { "math": [ "u_proficiency('prof_test', 'format': 'time_spent', 'direct': 'true')", "=", "time('24h')" ] }
+        "effect": { "math": [ "u_proficiency('prof_test', 'format': 'time_spent', 'direct': true)", "=", "time('24h')" ] }
       },
       {
         "text": "Learns Test Proficiency for 1h",
diff --git a/data/mods/TEST_DATA/EOC.json b/data/mods/TEST_DATA/EOC.json
index 1cb8566f9135f..fdb4692462f8f 100644
--- a/data/mods/TEST_DATA/EOC.json
+++ b/data/mods/TEST_DATA/EOC.json
@@ -338,15 +338,15 @@
     "effect": [
       { "set_string_var": "prof_test", "target_var": { "global_val": "prof_id" } },
       { "math": [ "key_total_time_required", "=", "u_proficiency(prof_id, 'format': 'total_time_required')" ] },
-      { "math": [ "u_proficiency(prof_id, 'direct': 'true')", "=", "50" ] },
+      { "math": [ "u_proficiency(prof_id, 'direct': true)", "=", "50" ] },
       { "math": [ "key_time_spent_50", "=", "u_proficiency(prof_id)" ] },
-      { "math": [ "u_proficiency(prof_id, 'format': 'percent', 'direct': 'true')", "=", "50" ] },
+      { "math": [ "u_proficiency(prof_id, 'format': 'percent', 'direct': true)", "=", "50" ] },
       { "math": [ "key_percent_50", "=", "u_proficiency(prof_id, 'format': 'percent')" ] },
       { "math": [ "key_percent_50_turn", "=", "u_proficiency(prof_id)" ] },
-      { "math": [ "u_proficiency(prof_id, 'format': 'permille', 'direct': 'true')", "=", "50" ] },
+      { "math": [ "u_proficiency(prof_id, 'format': 'permille', 'direct': true)", "=", "50" ] },
       { "math": [ "key_permille_50", "=", "u_proficiency(prof_id, 'format': 'permille')" ] },
       { "math": [ "key_permille_50_turn", "=", "u_proficiency(prof_id)" ] },
-      { "math": [ "u_proficiency(prof_id, 'format': 'time_left', 'direct': 'true')", "=", "50" ] },
+      { "math": [ "u_proficiency(prof_id, 'format': 'time_left', 'direct': true)", "=", "50" ] },
       { "math": [ "key_time_left_50", "=", "u_proficiency(prof_id, 'format': 'time_left')" ] },
       { "math": [ "key_time_left_50_turn", "=", "u_proficiency(prof_id)" ] }
     ]
diff --git a/doc/NPCs.md b/doc/NPCs.md
index 9590151e45579..b163f4f59dde5 100644
--- a/doc/NPCs.md
+++ b/doc/NPCs.md
@@ -1352,7 +1352,7 @@ _some functions support array arguments or kwargs, denoted with square brackets
 | moon_phase()     |  ✅  |   ❌   | N/A<br/>(global)  | Returns current phase of the Moon. <pre>MOON_NEW = 0,<br/>WAXING_CRESCENT = 1,<br/>HALF_MOON_WAXING = 2,<br/>WAXING_GIBBOUS = 3,<br/>FULL = 4,<br/>WANING_GIBBOUS = 5,<br/>HALF_MOON_WANING = 6,<br/>WANING_CRESCENT = 7 |
 | num_input(`s`/`v`,`d`/`v`)   |  ✅  |   ❌   | N/A<br/>(global)  | Prompt the player for a number.<br/>Arguments are Prompt text, Default Value:<br/>`"math": [ "u_value_to_set", "=", "num_input('Playstyle Perks Cost?', 4)" ]`|
 | pain()     |  ✅  |   ✅   | u, n  | Return or set pain<br/> Example:<br/>`{ "math": [ "n_pain()", "=", "u_pain() + 9000" ] }`|
-| proficiency(`s`/`v`)    |  ✅   |   ✅  | u, n  | Return or set proficiency<br/>Argument is proficiency ID.<br/><br/> Optional kwargs:<br/>`format`: `s` - `percent` return or set how many percent done the learning is. `permille` does likewise for permille. `time_spent` return or set total time spent. `time_left` return or set the remaining time. `total_time_required` return total time required to train a given proficiency (read only).<br/>`direct`: `s` - `false` (default) perform the adjustment by practicing the proficiency for the given amount of time. This will likely result in different values than specified. `true` perform the adjustment directly, bypassing other factors that may affect it.<br/><br/>Example:<br/>`{ "math": [ "u_proficiency('prof_intro_chemistry', 'format': 'percent')", "=", "50" ] }`|
+| proficiency(`s`/`v`)    |  ✅   |   ✅  | u, n  | Return or set proficiency<br/>Argument is proficiency ID.<br/><br/> Optional kwargs:<br/>`format`: `s` - `percent` return or set how many percent done the learning is. `permille` does likewise for permille. `time_spent` return or set total time spent. `time_left` return or set the remaining time. `total_time_required` return total time required to train a given proficiency (read only).<br/>`direct`: `true`/`false`/`d` - false (default) perform the adjustment by practicing the proficiency for the given amount of time. This will likely result in different values than specified. `true` perform the adjustment directly, bypassing other factors that may affect it.<br/><br/>Example:<br/>`{ "math": [ "u_proficiency('prof_intro_chemistry', 'format': 'percent')", "=", "50" ] }`|
 | school_level(`s`/`v`)    |  ✅   |   ❌  | u, n  | Return the highest level of spells known of that school.<br/>Argument is school ID.<br/><br/>Example:<br/>`"condition": { "math": [ "u_school_level('MAGUS')", ">=", "3"] }`|
 | school_level_adjustment(`s`/`v`)    |   ✅  |  ✅   | u, n  | Return or set temporary caster level adjustment. Only useable by EoCs that trigger on the event `opens_spellbook`. Old values will be reset to 0 before the event triggers. To avoid overwriting values from other EoCs, it is recommended to adjust the values here with `+=` or `-=` instead of setting it to an absolute value.<br/>Argument is school ID.<br/><br/>Example:<br/>`{ "math": [ "u_school_level_adjustment('MAGUS')", "+=", "3"] }`|
 | skill(`s`/`v`)    |  ✅  |   ✅   | u, n  | Return or set skill level<br/><br/>Example:<br/>`"condition": { "math": [ "u_skill('driving')", ">=", "5"] }`<br/>`"condition": { "math": [ "u_skill(someskill)", ">=", "5"] }`|
diff --git a/src/math_parser_diag.cpp b/src/math_parser_diag.cpp
index 0d57e8e4987de..146395375a472 100644
--- a/src/math_parser_diag.cpp
+++ b/src/math_parser_diag.cpp
@@ -66,6 +66,11 @@ bool is_beta( char scope )
     }
 }
 
+constexpr bool is_true( double dbl )
+{
+    return dbl >= 1 || float_equals( dbl, 1 );
+}
+
 template<typename T>
 constexpr std::string_view _str_type_of()
 {
@@ -1195,7 +1200,7 @@ std::function<void( dialogue &, double )> proficiency_ass( char scope,
         std::vector<diag_value> const &params, diag_kwargs const &kwargs )
 {
     diag_value fmt_val( std::string{"time_spent"} );
-    diag_value direct_val( std::string{"false"} );
+    diag_value direct_val( 0.0 );
     if( kwargs.count( "format" ) != 0 ) {
         fmt_val = *kwargs.at( "format" );
     }
@@ -1206,7 +1211,7 @@ std::function<void( dialogue &, double )> proficiency_ass( char scope,
     double val ) {
         proficiency_id prof( prof_value.str( d ) );
         std::string const format = fmt_val.str( d );
-        std::string direct = direct_val.str( d );
+        bool const direct = is_true( direct_val.dbl( d ) );
         int to_write = 0;
         if( format == "percent" ) {
             to_write = to_turns<int>( prof->time_to_learn() * val ) / 100;
@@ -1222,14 +1227,11 @@ std::function<void( dialogue &, double )> proficiency_ass( char scope,
         }
         int before = to_turns<int>( d.actor( beta )->proficiency_practiced_time( prof ) );
         int learned = to_write - before;
-        if( direct != "true" && direct != "false" ) {
-            debugmsg( R"(Unknown direct value "%s" for proficiency, assuming "false")", direct );
-            direct = "false";
-        } else if( direct == "false" && learned < 0 ) {
+        if( !direct && learned < 0 ) {
             debugmsg( "For proficiency %s in dialogue, trying to learn negative without direct", prof.str() );
             return 0;
         }
-        if( direct == "false" ) {
+        if( !direct ) {
             d.actor( beta )->train_proficiency_for( prof, learned );
         } else {
             d.actor( beta )->set_proficiency_practiced_time( prof, to_write );
diff --git a/src/math_parser_func.h b/src/math_parser_func.h
index a205790f76b9c..6c3a6febaed6e 100644
--- a/src/math_parser_func.h
+++ b/src/math_parser_func.h
@@ -171,10 +171,12 @@ constexpr double e_v = 2.7182818284590452354;
 #endif
 } // namespace math_constants
 
-constexpr std::array<math_const, 3> constants{
+constexpr std::array<math_const, 5> constants{
     math_const{ "π", math_constants::pi_v },
     math_const{ "pi", math_constants::pi_v },
     math_const{ "e", math_constants::e_v },
+    math_const{ "true", 1 },
+    math_const{ "false", 0 },
 };
 
 std::vector<std::string_view> tokenize( std::string_view str, std::string_view separators,
diff --git a/tests/npc_talk_test.cpp b/tests/npc_talk_test.cpp
index f1b6e9ccc69b0..5c581c9e77bc7 100644
--- a/tests/npc_talk_test.cpp
+++ b/tests/npc_talk_test.cpp
@@ -1495,7 +1495,7 @@ TEST_CASE( "npc_arithmetic", "[npc_talk]" )
                        proficiency_prof_test ) == 0 );
 
 
-    // Proficency learning without 'direct': 'true' is impacted by focus
+    // Proficency learning without 'direct': true is impacted by focus
     const auto prof_xp = [&player_character]() {
         return to_seconds<int>( player_character.get_proficiency_practiced_time( proficiency_prof_test ) );
     };