diff --git a/code/__DEFINES/skills/helpers.dm b/code/__DEFINES/skills/helpers.dm
index 9f1fbbf0e2..dde412fd7d 100644
--- a/code/__DEFINES/skills/helpers.dm
+++ b/code/__DEFINES/skills/helpers.dm
@@ -23,7 +23,7 @@
   * from/to new/old minds.
   */
 #define ADD_SKILL_MODIFIER_BODY(path, id, body, prototype) \
-	prototype = GLOB.skill_modifiers[GET_SKILL_MOD_ID(path, id)] || new path(id);\
+	prototype = GLOB.skill_modifiers[GET_SKILL_MOD_ID(path, id)] || new path(id, TRUE);\
 	if(body.mind){\
 		body.mind.add_skill_modifier(prototype.identifier)\
 	} else {\
@@ -43,6 +43,6 @@
 ///Macro used when adding generic singleton skill modifiers.
 #define ADD_SINGLETON_SKILL_MODIFIER(mind, path, id) \
 	if(!GLOB.skill_modifiers[GET_SKILL_MOD_ID(path, id)]){\
-		new path(id)\
+		new path(id, TRUE)\
 	};\
-	mind.add_skill_modifier(GET_SKILL_MOD_ID(path, id))
\ No newline at end of file
+	mind.add_skill_modifier(GET_SKILL_MOD_ID(path, id))
diff --git a/code/datums/skills/_skill_holder.dm b/code/datums/skills/_skill_holder.dm
index ecc7bb0878..500b49a1ff 100644
--- a/code/datums/skills/_skill_holder.dm
+++ b/code/datums/skills/_skill_holder.dm
@@ -52,7 +52,7 @@
 		for(var/k in L)
 			var/datum/skill_modifier/M = GLOB.skill_modifiers[k]
 			. = M.apply_modifier(., skill, skill_holder, MODIFIER_TARGET_LEVEL)
-		. = SANITIZE_SKILL_LEVEL(skill, round ? round(.) : .)
+		. = SANITIZE_SKILL_LEVEL(skill, round ? round(., 1) : .)
 
 /**
   * Grabs our affinity for a skill. !!This is a multiplier!!
diff --git a/code/datums/skills/_skill_modifier.dm b/code/datums/skills/_skill_modifier.dm
index e704e13dea..a2c9552871 100644
--- a/code/datums/skills/_skill_modifier.dm
+++ b/code/datums/skills/_skill_modifier.dm
@@ -10,7 +10,7 @@ GLOBAL_LIST_EMPTY(potential_mods_per_skill)
 	/// flags for this skill modifier.
 	var/modifier_flags = NONE
 	/// target skills, can be a specific skill typepath or a set of skill flags.
-	var/target_skills = ALL
+	var/target_skills = NONE
 	/// The identifier key this skill modifier is associated with.
 	var/identifier
 	/// skill affinity modifier, can be a multiplier or addendum, depending on the modifier_flags flags.
@@ -22,15 +22,21 @@ GLOBAL_LIST_EMPTY(potential_mods_per_skill)
 	/// Priority of this skill modifier compared to other ones.
 	var/priority = MODIFIER_SKILL_PRIORITY_DEF
 
-/datum/skill_modifier/New(id)
+/datum/skill_modifier/New(id, register = FALSE)
 	identifier = GET_SKILL_MOD_ID(type, id)
 	if(id)
 		var/former_id = identifier
 		var/dupe = 0
 		while(GLOB.skill_modifiers[identifier])
 			identifier = "[former_id][++dupe]"
-	GLOB.skill_modifiers[identifier] = src
 
+	if(register)
+		register()
+
+/datum/skill_modifier/proc/register()
+	if(GLOB.skill_modifiers[identifier])
+		CRASH("Skill modifier identifier \"[identifier]\" already taken.")
+	GLOB.skill_modifiers[identifier] = src
 	if(ispath(target_skills))
 		var/list/mod_L = GLOB.potential_mods_per_skill[target_skills]
 		if(!mod_L)
@@ -147,11 +153,13 @@ GLOBAL_LIST_EMPTY(potential_mods_per_skill)
 		if(MODIFIER_TARGET_AFFINITY)
 			mod = affinity_mod
 
+	var/diff = 0
 	if(modifier_flags & (MODIFIER_SKILL_VIRTUE|MODIFIER_SKILL_HANDICAP))
 		if(modifier_flags & MODIFIER_SKILL_VIRTUE)
 			. = max(., mod)
 		if(modifier_flags & MODIFIER_SKILL_HANDICAP)
 			. = min(., mod)
+		diff = . - mod
 	else if(modifier_flags & MODIFIER_SKILL_MULT)
 		. *= mod
 	else
@@ -164,7 +172,7 @@ GLOBAL_LIST_EMPTY(potential_mods_per_skill)
 				to_access = H.original_levels
 			if(MODIFIER_TARGET_AFFINITY)
 				to_access = H.original_affinities
-		. += value - LAZYACCESS(to_access[identifier], "[skillpath]")
+		. += value - diff - LAZYACCESS(to_access[identifier], "[skillpath]")
 
 ///Body bound modifier signal procs.
 /datum/skill_modifier/proc/on_mind_transfer(datum/mind/source, mob/new_character, mob/old_character)
diff --git a/code/datums/wires/_wires.dm b/code/datums/wires/_wires.dm
index e020afa47a..9df144b184 100644
--- a/code/datums/wires/_wires.dm
+++ b/code/datums/wires/_wires.dm
@@ -138,7 +138,7 @@
 	if(current_users[user])
 		return FALSE
 	if(req_skill && user?.mind)
-		var/level_diff = req_skill - user.mind.get_skill_level(/datum/skill/level/job/wiring)
+		var/level_diff = req_skill - user.mind.get_skill_level(/datum/skill/level/job/wiring, round = TRUE)
 		if(level_diff > 0)
 			LAZYSET(current_users, user, TRUE)
 			to_chat(user, "<span class='notice'>You begin cutting [holder]'s [color] wire...</span>")
@@ -167,7 +167,7 @@
 	if(current_users[user])
 		return FALSE
 	if(req_skill && user?.mind)
-		var/level_diff = req_skill - user.mind.get_skill_level(/datum/skill/level/job/wiring)
+		var/level_diff = req_skill - user.mind.get_skill_level(/datum/skill/level/job/wiring, round = TRUE)
 		if(level_diff > 0)
 			LAZYSET(current_users, user, TRUE)
 			to_chat(user, "<span class='notice'>You begin pulsing [holder]'s [color] wire...</span>")