diff --git a/man/rgblink.5 b/man/rgblink.5
index da1ed26e..245dfc57 100644
--- a/man/rgblink.5
+++ b/man/rgblink.5
@@ -24,18 +24,20 @@ They are simply ignored.
 .Pp
 Keywords are composed of letters and digits (but they can't start with a digit); they are all case-insensitive.
 .Pp
-Numbers can be written in decimal format, or in binary using the
-.Ql %
-prefix, or in hexadecimal using the
-.Ql $
-prefix (hexadecimal digits are case-insensitive).
-Note that unlike
-.Xr rgbasm 5 ,
-an octal
-.Ql &
-prefix is not supported, nor are
-.Ql _
-digit separators.
+Numbers can be written in a number of formats.
+.Bl -column -offset indent "Hexadecimal" "Possible prefixes"
+.It Sy Format type Ta Sy Possible prefixes Ta Sy Accepted characters
+.It Decimal Ta none Ta 0123456789
+.It Hexadecimal Ta Li $ , 0x , 0X Ta 0123456789ABCDEF
+.It Octal Ta Li & , 0o , 0O Ta 01234567
+.It Binary Ta Li % , 0b , 0B Ta 01
+.El
+.Pp
+Underscores are also accepted in numbers, except at the beginning of one.
+This can be useful for grouping digits, like
+.Ql 1_234
+or
+.Ql $ff_80 .
 .Pp
 Strings begin with a double quote, and end at the next (non-escaped) double quote.
 Strings must not contain literal newline characters.
@@ -46,8 +48,9 @@ are supported, specifically
 .Ql \e" ,
 .Ql \en ,
 .Ql \er ,
+.Ql \et ,
 and
-.Ql \et .
+.Ql \e0 .
 Other backslash escape sequences in
 .Xr rgbasm 5
 are only relevant to assembly code and do not apply in linker scripts.
diff --git a/src/link/script.y b/src/link/script.y
index 6cd4ecca..6e43332d 100644
--- a/src/link/script.y
+++ b/src/link/script.y
@@ -17,9 +17,9 @@
 	#include <algorithm>
 	#include <array>
 	#include <bit>
+	#include <ctype.h>
 	#include <fstream>
 	#include <inttypes.h>
-	#include <locale>
 	#include <stdio.h>
 	#include <string_view>
 	#include <vector>
@@ -209,18 +209,100 @@ static bool isNewline(int c) {
 	return c == '\r' || c == '\n';
 }
 
+static yy::parser::symbol_type yywrap() {
+	if (lexerStack.size() != 1) {
+		if (!atEof) {
+			// Inject a newline at EOF to simplify parsing.
+			atEof = true;
+			return yy::parser::make_newline();
+		}
+		lexerStack.pop_back();
+		return yylex();
+	}
+	if (!atEof) {
+		// Inject a newline at EOF to simplify parsing.
+		atEof = true;
+		return yy::parser::make_newline();
+	}
+	return yy::parser::make_YYEOF();
+}
+
 static bool isIdentChar(int c) {
 	return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9');
 }
 
+static std::string readIdent(int c) {
+	auto &context = lexerStack.back();
+	std::string ident;
+	ident.push_back(c);
+	for (c = context.file.sgetc(); isIdentChar(c); c = context.file.snextc()) {
+		ident.push_back(c);
+	}
+	return ident;
+}
+
 static bool isDecDigit(int c) {
 	return c >= '0' && c <= '9';
 }
 
+static yy::parser::symbol_type parseDecNumber(int c) {
+	auto &context = lexerStack.back();
+	uint32_t number = c - '0';
+	for (c = context.file.sgetc(); isDecDigit(c) || c == '_'; c = context.file.sgetc()) {
+		if (c != '_') {
+			number = number * 10 + (c - '0');
+		}
+		context.file.sbumpc();
+	}
+	return yy::parser::make_number(number);
+}
+
 static bool isBinDigit(int c) {
 	return c >= '0' && c <= '1';
 }
 
+static yy::parser::symbol_type parseBinNumber(char const *prefix) {
+	auto &context = lexerStack.back();
+	auto c = context.file.sgetc();
+	if (!isBinDigit(c)) {
+		scriptError(context, "No binary digits found after '%s'", prefix);
+		return yy::parser::make_number(0);
+	}
+
+	uint32_t number = c - '0';
+	context.file.sbumpc();
+	for (c = context.file.sgetc(); isBinDigit(c) || c == '_'; c = context.file.sgetc()) {
+		if (c != '_') {
+			number = number * 2 + (c - '0');
+		}
+		context.file.sbumpc();
+	}
+	return yy::parser::make_number(number);
+}
+
+static bool isOctDigit(int c) {
+	return c >= '0' && c <= '7';
+}
+
+static yy::parser::symbol_type parseOctNumber(char const *prefix) {
+	auto &context = lexerStack.back();
+	auto c = context.file.sgetc();
+	if (!isOctDigit(c)) {
+		scriptError(context, "No octal digits found after '%s'", prefix);
+		return yy::parser::make_number(0);
+	}
+
+	uint32_t number = c - '0';
+	context.file.sbumpc();
+	for (c = context.file.sgetc(); isOctDigit(c) || c == '_'; c = context.file.sgetc()) {
+		if (c != '_') {
+			number = number * 8 + (c - '0');
+		}
+		context.file.sbumpc();
+	}
+	return yy::parser::make_number(number);
+}
+
 static bool isHexDigit(int c) {
 	return (c >= '0' && c <= '9') || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f');
 }
@@ -237,6 +319,88 @@ static uint8_t parseHexDigit(int c) {
 	}
 }
 
+static yy::parser::symbol_type parseHexNumber(char const *prefix) {
+	auto &context = lexerStack.back();
+	auto c = context.file.sgetc();
+	if (!isHexDigit(c)) {
+		scriptError(context, "No hexadecimal digits found after '%s'", prefix);
+		return yy::parser::make_number(0);
+	}
+
+	uint32_t number = parseHexDigit(c);
+	context.file.sbumpc();
+	for (c = context.file.sgetc(); isHexDigit(c) || c == '_'; c = context.file.sgetc()) {
+		if (c != '_') {
+			number = number * 16 + parseHexDigit(c);
+		}
+		context.file.sbumpc();
+	}
+	return yy::parser::make_number(number);
+}
+
+static yy::parser::symbol_type parseNumber(int c) {
+	auto &context = lexerStack.back();
+	if (c == '0') {
+		switch (context.file.sgetc()) {
+		case 'x':
+			context.file.sbumpc();
+			return parseHexNumber("0x");
+		case 'X':
+			context.file.sbumpc();
+			return parseHexNumber("0X");
+		case 'o':
+			context.file.sbumpc();
+			return parseOctNumber("0o");
+		case 'O':
+			context.file.sbumpc();
+			return parseOctNumber("0O");
+		case 'b':
+			context.file.sbumpc();
+			return parseBinNumber("0b");
+		case 'B':
+			context.file.sbumpc();
+			return parseBinNumber("0B");
+		}
+	}
+	return parseDecNumber(c);
+}
+
+static yy::parser::symbol_type parseString() {
+	auto &context = lexerStack.back();
+	auto c = context.file.sgetc();
+	std::string str;
+	for (; c != '"'; c = context.file.sgetc()) {
+		if (c == EOF || isNewline(c)) {
+			scriptError(context, "Unterminated string");
+			break;
+		}
+		context.file.sbumpc();
+		if (c == '\\') {
+			c = context.file.sgetc();
+			if (c == EOF || isNewline(c)) {
+				scriptError(context, "Unterminated string");
+				break;
+			} else if (c == 'n') {
+				c = '\n';
+			} else if (c == 'r') {
+				c = '\r';
+			} else if (c == 't') {
+				c = '\t';
+			} else if (c == '0') {
+				c = '\0';
+			} else if (c != '\\' && c != '"' && c != '\'') {
+				scriptError(context, "Cannot escape character %s", printChar(c));
+			}
+			context.file.sbumpc();
+		}
+		str.push_back(c);
+	}
+	if (c == '"') {
+		context.file.sbumpc();
+	}
+	return yy::parser::make_string(std::move(str));
+}
+
 yy::parser::symbol_type yylex() {
 	auto &context = lexerStack.back();
 	auto c = context.file.sbumpc();
@@ -254,23 +418,7 @@ yy::parser::symbol_type yylex() {
 
 	// Alright, what token should we return?
 	if (c == EOF) {
-		// Basically yywrap().
-		if (lexerStack.size() != 1) {
-			if (!atEof) {
-				// Inject a newline at EOF to simplify parsing.
-				atEof = true;
-				return yy::parser::make_newline();
-			} else {
-				lexerStack.pop_back();
-				return yylex();
-			}
-		} else if (!atEof) {
-			// Inject a newline at EOF to simplify parsing.
-			atEof = true;
-			return yy::parser::make_newline();
-		} else {
-			return yy::parser::make_YYEOF();
-		}
+		return yywrap();
 	} else if (c == ',') {
 		return yy::parser::make_COMMA();
 	} else if (isNewline(c)) {
@@ -280,85 +428,21 @@ yy::parser::symbol_type yylex() {
 		}
 		return yy::parser::make_newline();
 	} else if (c == '"') {
-		std::string str;
-
-		for (c = context.file.sgetc(); c != '"'; c = context.file.sgetc()) {
-			if (c == EOF || isNewline(c)) {
-				scriptError(context, "Unterminated string");
-				break;
-			}
-			context.file.sbumpc();
-			if (c == '\\') {
-				c = context.file.sgetc();
-				if (c == EOF || isNewline(c)) {
-					scriptError(context, "Unterminated string");
-					break;
-				} else if (c == 'n') {
-					c = '\n';
-				} else if (c == 'r') {
-					c = '\r';
-				} else if (c == 't') {
-					c = '\t';
-				} else if (c != '\\' && c != '"' && c != '\'') {
-					scriptError(context, "Cannot escape character %s", printChar(c));
-				}
-				context.file.sbumpc();
-			}
-			str.push_back(c);
-		}
-		if (c == '"') {
-			context.file.sbumpc();
-		}
-
-		return yy::parser::make_string(std::move(str));
+		return parseString();
 	} else if (c == '$') {
-		c = context.file.sgetc();
-		if (!isHexDigit(c)) {
-			scriptError(context, "No hexadecimal digits found after '$'");
-			return yy::parser::make_number(0);
-		}
-
-		uint32_t number = parseHexDigit(c);
-		context.file.sbumpc();
-		for (c = context.file.sgetc(); isHexDigit(c); c = context.file.sgetc()) {
-			number = number * 16 + parseHexDigit(c);
-			context.file.sbumpc();
-		}
-		return yy::parser::make_number(number);
+		return parseHexNumber("$");
 	} else if (c == '%') {
-		c = context.file.sgetc();
-		if (!isBinDigit(c)) {
-			scriptError(context, "No binary digits found after '%%'");
-			return yy::parser::make_number(0);
-		}
-
-		uint32_t number = c - '0';
-		context.file.sbumpc();
-		for (c = context.file.sgetc(); isBinDigit(c); c = context.file.sgetc()) {
-			number = number * 2 + (c - '0');
-			context.file.sbumpc();
-		}
-		return yy::parser::make_number(number);
+		return parseBinNumber("%");
+	} else if (c == '&') {
+		return parseOctNumber("&");
 	} else if (isDecDigit(c)) {
-		uint32_t number = c - '0';
-		for (c = context.file.sgetc(); isDecDigit(c); c = context.file.sgetc()) {
-			number = number * 10 + (c - '0');
-			context.file.sbumpc();
-		}
-		return yy::parser::make_number(number);
+		return parseNumber(c);
 	} else if (isIdentChar(c)) { // Note that we match these *after* digit characters!
-		std::string ident;
-		auto strUpperCmp = [](char cmp, char ref) {
-			// `locale::classic()` yields the "C" locale.
-			assume(!std::use_facet<std::ctype<char>>(std::locale::classic())
-			            .is(std::ctype_base::lower, ref));
-			return std::use_facet<std::ctype<char>>(std::locale::classic()).toupper(cmp) == ref;
-		};
+		std::string ident = readIdent(c);
 
-		ident.push_back(c);
-		for (c = context.file.sgetc(); isIdentChar(c); c = context.file.snextc()) {
-			ident.push_back(c);
-		}
+		auto strUpperCmp = [](char cmp, char ref) {
+			return toupper(cmp) == ref;
+		};
 
 		for (SectionType type : EnumSeq(SECTTYPE_INVALID)) {
 			if (std::equal(RANGE(ident), RANGE(sectionTypeInfo[type].name), strUpperCmp)) {
diff --git a/test/link/script-num-fmt.link b/test/link/script-num-fmt.link
index 1465027b..09386e9f 100644
--- a/test/link/script-num-fmt.link
+++ b/test/link/script-num-fmt.link
@@ -1,5 +1,9 @@
 ROM0
-	org 42
-	org %101010
-	org $2A
+	org 4_2
+	org %10_10_10
+	org &52_
+	org $2A_
+	org 0b101_010
+	org 0o5_2
+	org 0x2_A
 	org 41 ; Error!
diff --git a/test/link/script-num-fmt.out b/test/link/script-num-fmt.out
index 6e3ca3ec..3ea2a44a 100644
--- a/test/link/script-num-fmt.out
+++ b/test/link/script-num-fmt.out
@@ -1,2 +1,2 @@
-error: script-num-fmt.link(5): Cannot decrease the current address (from $002a to $0029)
+error: script-num-fmt.link(9): Cannot decrease the current address (from $002a to $0029)
 Linking failed with 1 error
diff --git a/test/link/script-okay.link b/test/link/script-okay.link
new file mode 100644
index 00000000..5a5014fc
--- /dev/null
+++ b/test/link/script-okay.link
@@ -0,0 +1,8 @@
+ROM0
+	"ROM0"
+	"\\\"\'\n\r\t\0"
+ROMX 1
+	"ROM1"
+ROMX 2
+	"ROM2 1K"
+	"ROM2 1"
diff --git a/test/link/script-okay.out b/test/link/script-okay.out
new file mode 100644
index 00000000..e69de29b
diff --git a/test/link/script.asm b/test/link/script.asm
index 1b272ba5..44f175c9 100644
--- a/test/link/script.asm
+++ b/test/link/script.asm
@@ -7,3 +7,4 @@ SECTION "ROM2 1K", ROMX,BANK[2]
 	ds $1000
 SECTION "ROM2 1", ROMX,BANK[2]
 	ds 1
+SECTION "\\\"\'\n\r\t\0", ROM0