diff --git a/fusee/fusee-primary/src/lib/vsprintf.c b/fusee/fusee-primary/src/lib/vsprintf.c
index c646f9f90..0dd4c4514 100644
--- a/fusee/fusee-primary/src/lib/vsprintf.c
+++ b/fusee/fusee-primary/src/lib/vsprintf.c
@@ -1577,10 +1577,10 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 			digit = *(str + 1);
 
 		if (!digit
-		    || (base == 16 && !isxdigit(digit))
-		    || (base == 10 && !isdigit(digit))
-		    || (base == 8 && (!isdigit(digit) || digit > '7'))
-		    || (base == 0 && !isdigit(digit)))
+		    || (base == 16 && !isxdigit((unsigned char)digit))
+		    || (base == 10 && !isdigit((unsigned char)digit))
+		    || (base == 8 && (!isdigit((unsigned char)digit) || digit > '7'))
+		    || (base == 0 && !isdigit((unsigned char)digit)))
 			break;
 
 		switch (qualifier) {
diff --git a/fusee/fusee-secondary/src/ips.c b/fusee/fusee-secondary/src/ips.c
index dedd00c67..8d36772f4 100644
--- a/fusee/fusee-secondary/src/ips.c
+++ b/fusee/fusee-secondary/src/ips.c
@@ -176,7 +176,7 @@ static inline uint8_t hex_nybble_to_u8(const char nybble) {
 static bool name_matches_hash(const char *name, size_t name_len, const void *hash, size_t hash_size) {
     /* Validate name is hex build id. */
     for (unsigned int i = 0; i < name_len - 4; i++) {
-        if (isxdigit(name[i]) == 0) {
+        if (isxdigit((unsigned char)name[i]) == 0) {
                 return false;
         }
     }
diff --git a/sept/sept-secondary/src/lib/vsprintf.c b/sept/sept-secondary/src/lib/vsprintf.c
index d934144c9..7927c83a2 100644
--- a/sept/sept-secondary/src/lib/vsprintf.c
+++ b/sept/sept-secondary/src/lib/vsprintf.c
@@ -83,7 +83,7 @@ static char *skip_spaces(const char *str)
 static unsigned int simple_guess_base(const char *cp)
 {
 	if (cp[0] == '0') {
-		if (TOLOWER(cp[1]) == 'x' && isxdigit(cp[2]))
+		if (TOLOWER(cp[1]) == 'x' && isxdigit((unsigned char)cp[2]))
 			return 16;
 		else
 			return 8;
@@ -108,10 +108,10 @@ unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int bas
 	if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
 		cp += 2;
 
-	while (isxdigit(*cp)) {
+	while (isxdigit((unsigned char)*cp)) {
 		unsigned int value;
 
-		value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
+		value = isdigit((unsigned char)*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
 		if (value >= base)
 			break;
 		result = result * base + value;
@@ -167,7 +167,7 @@ int skip_atoi(const char **s)
 {
 	int i = 0;
 
-	while (isdigit(**s))
+	while (isdigit((unsigned char)**s))
 		i = i*10 + *((*s)++) - '0';
 
 	return i;
@@ -654,7 +654,7 @@ int format_decode(const char *fmt, struct printf_spec *spec)
 	/* get field width */
 	spec->field_width = -1;
 
-	if (isdigit(*fmt))
+	if (isdigit((unsigned char)*fmt))
 		spec->field_width = skip_atoi(&fmt);
 	else if (*fmt == '*') {
 		/* it's the next argument */
@@ -667,7 +667,7 @@ precision:
 	spec->precision = -1;
 	if (*fmt == '.') {
 		++fmt;
-		if (isdigit(*fmt)) {
+		if (isdigit((unsigned char)*fmt)) {
 			spec->precision = skip_atoi(&fmt);
 			if (spec->precision < 0)
 				spec->precision = 0;
@@ -1485,7 +1485,7 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 
 		/* get field width */
 		field_width = -1;
-		if (isdigit(*fmt))
+		if (isdigit((unsigned char)*fmt))
 			field_width = skip_atoi(&fmt);
 
 		/* get conversion qualifier */
@@ -1577,10 +1577,10 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 			digit = *(str + 1);
 
 		if (!digit
-		    || (base == 16 && !isxdigit(digit))
-		    || (base == 10 && !isdigit(digit))
-		    || (base == 8 && (!isdigit(digit) || digit > '7'))
-		    || (base == 0 && !isdigit(digit)))
+		    || (base == 16 && !isxdigit((unsigned char)digit))
+		    || (base == 10 && !isdigit((unsigned char)digit))
+		    || (base == 8 && (!isdigit((unsigned char)digit) || digit > '7'))
+		    || (base == 0 && !isdigit((unsigned char)digit)))
 			break;
 
 		switch (qualifier) {
diff --git a/stratosphere/ams_mitm/source/set_mitm/setsys_settings_items.cpp b/stratosphere/ams_mitm/source/set_mitm/setsys_settings_items.cpp
index 561cc32dc..34a00ce5b 100644
--- a/stratosphere/ams_mitm/source/set_mitm/setsys_settings_items.cpp
+++ b/stratosphere/ams_mitm/source/set_mitm/setsys_settings_items.cpp
@@ -116,7 +116,7 @@ Result SettingsItemManager::ValidateKey(const char *key) {
 
 static bool IsHexadecimal(const char *str) {
     while (*str) {
-        if (isxdigit(*str)) {
+        if (isxdigit((unsigned char)*str)) {
             str++;
         } else {
             return false;
diff --git a/stratosphere/ams_mitm/source/utils.cpp b/stratosphere/ams_mitm/source/utils.cpp
index 96b38d4a3..46e9fe236 100644
--- a/stratosphere/ams_mitm/source/utils.cpp
+++ b/stratosphere/ams_mitm/source/utils.cpp
@@ -70,7 +70,7 @@ static FsFile g_emummc_file = {0};
 
 static bool IsHexadecimal(const char *str) {
     while (*str) {
-        if (isxdigit(*str)) {
+        if (isxdigit((unsigned char)*str)) {
             str++;
         } else {
             return false;
diff --git a/stratosphere/dmnt/source/dmnt_cheat_manager.cpp b/stratosphere/dmnt/source/dmnt_cheat_manager.cpp
index 87d0a69ee..aaa1ee41c 100644
--- a/stratosphere/dmnt/source/dmnt_cheat_manager.cpp
+++ b/stratosphere/dmnt/source/dmnt_cheat_manager.cpp
@@ -349,7 +349,7 @@ bool DmntCheatManager::ParseCheats(const char *s, size_t len) {
 
             /* Skip onwards. */
             i = j + 1;
-        } else if (isxdigit(s[i])) {
+        } else if (isxdigit((unsigned char)s[i])) {
             /* Make sure that we have a cheat open. */
             if (cur_entry == NULL) {
                 return false;
@@ -363,7 +363,7 @@ bool DmntCheatManager::ParseCheats(const char *s, size_t len) {
             /* We're parsing an instruction, so validate it's 8 hex digits. */
             for (size_t j = 1; j < 8; j++) {
                 /* Validate 8 hex chars. */
-                if (i + j >= len || !isxdigit(s[i+j])) {
+                if (i + j >= len || !isxdigit((unsigned char)s[i+j])) {
                     return false;
                 }
             }
diff --git a/stratosphere/loader/source/ldr_ro_manager.cpp b/stratosphere/loader/source/ldr_ro_manager.cpp
index c1d9ce65d..10f610ae8 100644
--- a/stratosphere/loader/source/ldr_ro_manager.cpp
+++ b/stratosphere/loader/source/ldr_ro_manager.cpp
@@ -136,13 +136,14 @@ namespace sts::ldr::ro {
         /* Nintendo doesn't actually care about successful allocation. */
         for (size_t i = 0; i < ModuleCountMax; i++) {
             ModuleInfo *module = &info->modules[i];
-            if (!module->in_use) {
+            if (module->in_use) {
                 continue;
             }
 
             std::memcpy(module->info.build_id, build_id, sizeof(module->info.build_id));
             module->info.base_address = address;
             module->info.size = size;
+            module->in_use = true;
             break;
         }
 
diff --git a/stratosphere/pm/source/pm_boot2.cpp b/stratosphere/pm/source/pm_boot2.cpp
index dfa89f4ad..96ca703b5 100644
--- a/stratosphere/pm/source/pm_boot2.cpp
+++ b/stratosphere/pm/source/pm_boot2.cpp
@@ -32,7 +32,7 @@
 
 static bool IsHexadecimal(const char *str) {
     while (*str) {
-        if (isxdigit(*str)) {
+        if (isxdigit((unsigned char)*str)) {
             str++;
         } else {
             return false;
diff --git a/thermosphere/src/lib/vsprintf.c b/thermosphere/src/lib/vsprintf.c
index d934144c9..7927c83a2 100644
--- a/thermosphere/src/lib/vsprintf.c
+++ b/thermosphere/src/lib/vsprintf.c
@@ -83,7 +83,7 @@ static char *skip_spaces(const char *str)
 static unsigned int simple_guess_base(const char *cp)
 {
 	if (cp[0] == '0') {
-		if (TOLOWER(cp[1]) == 'x' && isxdigit(cp[2]))
+		if (TOLOWER(cp[1]) == 'x' && isxdigit((unsigned char)cp[2]))
 			return 16;
 		else
 			return 8;
@@ -108,10 +108,10 @@ unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int bas
 	if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
 		cp += 2;
 
-	while (isxdigit(*cp)) {
+	while (isxdigit((unsigned char)*cp)) {
 		unsigned int value;
 
-		value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
+		value = isdigit((unsigned char)*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
 		if (value >= base)
 			break;
 		result = result * base + value;
@@ -167,7 +167,7 @@ int skip_atoi(const char **s)
 {
 	int i = 0;
 
-	while (isdigit(**s))
+	while (isdigit((unsigned char)**s))
 		i = i*10 + *((*s)++) - '0';
 
 	return i;
@@ -654,7 +654,7 @@ int format_decode(const char *fmt, struct printf_spec *spec)
 	/* get field width */
 	spec->field_width = -1;
 
-	if (isdigit(*fmt))
+	if (isdigit((unsigned char)*fmt))
 		spec->field_width = skip_atoi(&fmt);
 	else if (*fmt == '*') {
 		/* it's the next argument */
@@ -667,7 +667,7 @@ precision:
 	spec->precision = -1;
 	if (*fmt == '.') {
 		++fmt;
-		if (isdigit(*fmt)) {
+		if (isdigit((unsigned char)*fmt)) {
 			spec->precision = skip_atoi(&fmt);
 			if (spec->precision < 0)
 				spec->precision = 0;
@@ -1485,7 +1485,7 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 
 		/* get field width */
 		field_width = -1;
-		if (isdigit(*fmt))
+		if (isdigit((unsigned char)*fmt))
 			field_width = skip_atoi(&fmt);
 
 		/* get conversion qualifier */
@@ -1577,10 +1577,10 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 			digit = *(str + 1);
 
 		if (!digit
-		    || (base == 16 && !isxdigit(digit))
-		    || (base == 10 && !isdigit(digit))
-		    || (base == 8 && (!isdigit(digit) || digit > '7'))
-		    || (base == 0 && !isdigit(digit)))
+		    || (base == 16 && !isxdigit((unsigned char)digit))
+		    || (base == 10 && !isdigit((unsigned char)digit))
+		    || (base == 8 && (!isdigit((unsigned char)digit) || digit > '7'))
+		    || (base == 0 && !isdigit((unsigned char)digit)))
 			break;
 
 		switch (qualifier) {