diff --git a/src/core/linebuf.c b/src/core/linebuf.c
index 7930d19a..c197e383 100644
--- a/src/core/linebuf.c
+++ b/src/core/linebuf.c
@@ -43,7 +43,18 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  * @ret line		Buffered line, or NULL if no line ready to read
  */
 char * buffered_line ( struct line_buffer *linebuf ) {
-	return ( linebuf->ready ? linebuf->data : NULL );
+	char *line = &linebuf->data[ linebuf->len ];
+
+	/* Fail unless we have a newly completed line to retrieve */
+	if ( ( linebuf->len == 0 ) || ( linebuf->consumed == 0 ) ||
+	     ( *(--line) != '\0' ) )
+		return NULL;
+
+	/* Identify start of line */
+	while ( ( line > linebuf->data ) && ( line[-1] != '\0' ) )
+		line--;
+
+	return line;
 }
 
 /**
@@ -52,10 +63,11 @@ char * buffered_line ( struct line_buffer *linebuf ) {
  * @v linebuf		Line buffer
  */
 void empty_line_buffer ( struct line_buffer *linebuf ) {
+
 	free ( linebuf->data );
 	linebuf->data = NULL;
 	linebuf->len = 0;
-	linebuf->ready = 0;
+	linebuf->consumed = 0;
 }
 
 /**
@@ -76,16 +88,13 @@ void empty_line_buffer ( struct line_buffer *linebuf ) {
  * should call empty_line_buffer() before freeing a @c struct @c
  * line_buffer.
  */
-ssize_t line_buffer ( struct line_buffer *linebuf,
-		      const char *data, size_t len ) {
+int line_buffer ( struct line_buffer *linebuf, const char *data, size_t len ) {
 	const char *eol;
 	size_t consume;
 	size_t new_len;
 	char *new_data;
-
-	/* Free any completed line from previous iteration */
-	if ( linebuf->ready )
-		empty_line_buffer ( linebuf );
+	char *lf;
+	char *cr;
 
 	/* Search for line terminator */
 	if ( ( eol = memchr ( data, '\n', len ) ) ) {
@@ -94,6 +103,10 @@ ssize_t line_buffer ( struct line_buffer *linebuf,
 		consume = len;
 	}
 
+	/* Reject any embedded NULs within the data to be consumed */
+	if ( memchr ( data, '\0', consume ) )
+		return -EINVAL;
+
 	/* Reallocate data buffer and copy in new data */
 	new_len = ( linebuf->len + consume );
 	new_data = realloc ( linebuf->data, ( new_len + 1 ) );
@@ -104,13 +117,27 @@ ssize_t line_buffer ( struct line_buffer *linebuf,
 	linebuf->data = new_data;
 	linebuf->len = new_len;
 
-	/* If we have reached end of line, trim the line and mark as ready */
+	/* If we have reached end of line, terminate the line */
 	if ( eol ) {
-		linebuf->data[--linebuf->len] = '\0'; /* trim NL */
-		if ( linebuf->data[linebuf->len - 1] == '\r' )
-			linebuf->data[--linebuf->len] = '\0'; /* trim CR */
-		linebuf->ready = 1;
+
+		/* Overwrite trailing LF (which must exist at this point) */
+		assert ( linebuf->len > 0 );
+		lf = &linebuf->data[ linebuf->len - 1 ];
+		assert ( *lf == '\n' );
+		*lf = '\0';
+
+		/* Trim (and overwrite) trailing CR, if present */
+		if ( linebuf->len > 1 ) {
+			cr = ( lf - 1 );
+			if ( *cr == '\r' ) {
+				linebuf->len--;
+				*cr = '\0';
+			}
+		}
 	}
 
+	/* Record consumed length */
+	linebuf->consumed = consume;
+
 	return consume;
 }
diff --git a/src/include/ipxe/linebuf.h b/src/include/ipxe/linebuf.h
index a1d56bbf..630278a0 100644
--- a/src/include/ipxe/linebuf.h
+++ b/src/include/ipxe/linebuf.h
@@ -14,17 +14,17 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 /** A line buffer */
 struct line_buffer {
-	/** Current string in the buffer */
+	/** Data buffer */
 	char *data;
-	/** Length of current string, excluding the terminating NUL */
+	/** Length of buffered data */
 	size_t len;
-	/** String is ready to read */
-	int ready;
+	/** Most recently consumed length */
+	size_t consumed;
 };
 
 extern char * buffered_line ( struct line_buffer *linebuf );
-extern ssize_t line_buffer ( struct line_buffer *linebuf,
-			     const char *data, size_t len );
+extern int line_buffer ( struct line_buffer *linebuf,
+			 const char *data, size_t len );
 extern void empty_line_buffer ( struct line_buffer *linebuf );
 
 #endif /* _IPXE_LINEBUF_H */
diff --git a/src/tests/linebuf_test.c b/src/tests/linebuf_test.c
index e06ac7d8..0dd486e9 100644
--- a/src/tests/linebuf_test.c
+++ b/src/tests/linebuf_test.c
@@ -1,35 +1,320 @@
-#include <stdint.h>
+/*
+ * Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** @file
+ *
+ * Line buffer self-tests
+ *
+ */
+
+/* Forcibly enable assertions */
+#undef NDEBUG
+
 #include <string.h>
-#include <stdio.h>
+#include <assert.h>
 #include <ipxe/linebuf.h>
+#include <ipxe/test.h>
 
-static const char data1[] = 
-"Hello world\r\n"
-"This is a reasonably nice set of lines\n"
-"with not many different terminators\r\n\r\n"
-"There should be exactly one blank line above\n"
-"and this line should never appear at all since it has no terminator";
+/** Define inline raw data */
+#define DATA(...) { __VA_ARGS__ }
 
-void linebuf_test ( void ) {
-	struct line_buffer linebuf;
-	const char *data = data1;
-	size_t len = ( sizeof ( data1 ) - 1 /* be mean; strip the NUL */ );
-	ssize_t frag_len;
-	char *line;
+/** Define inline lines */
+#define LINES(...) { __VA_ARGS__ }
 
-	memset ( &linebuf, 0, sizeof ( linebuf ) );
-	while ( len ) {
-		frag_len = line_buffer ( &linebuf, data, len );
-		if ( frag_len < 0 ) {
-			printf ( "line_buffer() failed: %s\n",
-				 strerror ( frag_len ) );
-			return;
-		}
-		data += frag_len;
-		len -= frag_len;
-		if ( ( line = buffered_line ( &linebuf ) ) )
-			printf ( "\"%s\"\n", line );
+/** A line buffer test */
+struct linebuf_test {
+	/** Raw data */
+	const void *data;
+	/** Length of raw data */
+	size_t len;
+	/** Expected sequence of lines */
+	const char **lines;
+	/** Number of expected lines */
+	unsigned int count;
+};
+
+/** Line buffer test expected failure indicator */
+static const char linebuf_failure[1];
+
+/**
+ * Define a line buffer test
+ *
+ * @v name		Test name
+ * @v DATA		Raw data
+ * @v LINES		Expected sequence of lines
+ * @ret test		Line buffer test
+ */
+#define LINEBUF_TEST( name, DATA, LINES )				\
+	static const char name ## _data[] = DATA;			\
+	static const char * name ## _lines[] = LINES;			\
+	static struct linebuf_test name = {				\
+		.data = name ## _data,					\
+		.len = ( sizeof ( name ## _data ) - 1 /* NUL */ ),	\
+		.lines = name ## _lines,				\
+		.count = ( sizeof ( name ## _lines ) /			\
+			   sizeof ( name ## _lines[0] ) ),		\
 	}
 
-	empty_line_buffer ( &linebuf );
+/** Simple line buffer test */
+LINEBUF_TEST ( simple,
+	       ( "HTTP/1.1 200 OK\r\n"
+		 "Content-Length: 123\r\n"
+		 "Content-Type: text/plain\r\n"
+		 "\r\n" ),
+	       LINES ( "HTTP/1.1 200 OK",
+		       "Content-Length: 123",
+		       "Content-Type: text/plain",
+		       "" ) );
+
+/** Mixed line terminators */
+LINEBUF_TEST ( mixed,
+	       ( "LF only\n" "CRLF\r\n" "\n" "\n" "\r\n" "\r\n" "CR only\r" ),
+	       LINES ( "LF only", "CRLF", "", "", "", "",
+		       NULL /* \r should not be treated as a terminator */ ) );
+
+/** Split consumption: part 1 */
+LINEBUF_TEST ( split_1,
+	       ( "This line was" ),
+	       LINES ( NULL ) );
+
+/** Split consumption: part 2 */
+LINEBUF_TEST ( split_2,
+	       ( " split across" ),
+	       LINES ( NULL ) );
+
+/** Split consumption: part 3 */
+LINEBUF_TEST ( split_3,
+	       ( " multiple calls\r\nand so was this one\r" ),
+	       LINES ( "This line was split across multiple calls", NULL ) );
+
+/** Split consumption: part 4 */
+LINEBUF_TEST ( split_4,
+	       ( "\nbut not this one\r\n" ),
+	       LINES ( "and so was this one", "but not this one" ) );
+
+/** Split consumption: part 5 */
+LINEBUF_TEST ( split_5,
+	       ( "" ),
+	       LINES ( NULL ) );
+
+/** Split consumption: part 6 */
+LINEBUF_TEST ( split_6,
+	       ( "This line came after a zero-length call\r\n" ),
+	       LINES ( "This line came after a zero-length call" ) );
+
+/** Embedded NULs */
+LINEBUF_TEST ( embedded_nuls,
+	       ( "This\r\ntest\r\nincludes\r\n\r\nsome\0binary\0data\r\n" ),
+	       LINES ( "This", "test", "includes", "", linebuf_failure ) );
+
+/**
+ * Report line buffer initialisation test result
+ *
+ * @v linebuf		Line buffer
+ * @v file		Test code file
+ * @v line		Test code line
+ */
+static void linebuf_init_okx ( struct line_buffer *linebuf,
+				const char *file, unsigned int line ) {
+
+	/* Initialise line buffer */
+	memset ( linebuf, 0, sizeof ( *linebuf ) );
+	okx ( buffered_line ( linebuf ) == NULL, file, line );
 }
+#define linebuf_init_ok( linebuf ) \
+	linebuf_init_okx ( linebuf, __FILE__, __LINE__ )
+
+/**
+ * Report line buffer consumption test result
+ *
+ * @v test		Line buffer test
+ * @v linebuf		Line buffer
+ * @v file		Test code file
+ * @v line		Test code line
+ */
+static void linebuf_consume_okx ( struct linebuf_test *test,
+				  struct line_buffer *linebuf,
+				  const char *file, unsigned int line ) {
+	const char *data = test->data;
+	size_t remaining = test->len;
+	int len;
+	unsigned int i;
+	const char *expected;
+	char *actual;
+	int rc;
+
+	DBGC ( test, "LINEBUF %p:\n", test );
+	DBGC_HDA ( test, 0, data, remaining );
+
+	/* Consume data one line at a time */
+	for ( i = 0 ; i < test->count ; i++ ) {
+
+		/* Add data to line buffer */
+		len = line_buffer ( linebuf, data, remaining );
+
+		/* Get buffered line, if any */
+		actual = buffered_line ( linebuf );
+		if ( len < 0 ) {
+			rc = len;
+			DBGC ( test, "LINEBUF %p %s\n", test, strerror ( rc ) );
+		} else if ( actual != NULL ) {
+			DBGC ( test, "LINEBUF %p \"%s\" (consumed %d)\n",
+			       test, actual, len );
+		} else {
+			DBGC ( test, "LINEBUF %p unterminated (consumed %d)\n",
+			       test, len );
+		}
+
+		/* Check for success/failure */
+		expected = test->lines[i];
+		if ( expected == linebuf_failure ) {
+			rc = len;
+			okx ( rc < 0, file, line );
+			okx ( remaining > 0, file, line );
+			return;
+		}
+		okx ( len >= 0, file, line );
+		okx ( ( ( size_t ) len ) <= remaining, file, line );
+
+		/* Check expected result */
+		if ( expected == NULL ) {
+			okx ( actual == NULL, file, line );
+		} else {
+			okx ( actual != NULL, file, line );
+			okx ( strcmp ( actual, expected ) == 0, file, line );
+		}
+
+		/* Consume data */
+		data += len;
+		remaining -= len;
+	}
+
+	/* Check that all data was consumed */
+	okx ( remaining == 0, file, line );
+}
+#define linebuf_consume_ok( test, linebuf ) \
+	linebuf_consume_okx ( test, linebuf, __FILE__, __LINE__ )
+
+/**
+ * Report line buffer accumulation test result
+ *
+ * @v test		Line buffer test
+ * @v linebuf		Line buffer
+ * @v file		Test code file
+ * @v line		Test code line
+ */
+static void linebuf_accumulated_okx ( struct linebuf_test *test,
+				      struct line_buffer *linebuf,
+				      const char *file, unsigned int line ) {
+	const char *actual;
+	const char *expected;
+	unsigned int i;
+
+	/* Check each accumulated line */
+	actual = linebuf->data;
+	for ( i = 0 ; i < test->count ; i++ ) {
+
+		/* Check accumulated line */
+		okx ( actual != NULL, file, line );
+		okx ( actual >= linebuf->data, file, line );
+		expected = test->lines[i];
+		if ( ( expected == NULL ) || ( expected == linebuf_failure ) )
+			return;
+		okx ( strcmp ( actual, expected ) == 0, file, line );
+
+		/* Move to next line */
+		actual += ( strlen ( actual ) + 1 /* NUL */ );
+		okx ( actual <= ( linebuf->data + linebuf->len ), file, line );
+	}
+}
+#define linebuf_accumulated_ok( test, linebuf ) \
+	linebuf_accumulated_okx ( test, linebuf, __FILE__, __LINE__ )
+
+/**
+ * Report line buffer emptying test result
+ *
+ * @v linebuf		Line buffer
+ * @v file		Test code file
+ * @v line		Test code line
+ */
+static void linebuf_empty_okx ( struct line_buffer *linebuf,
+				const char *file, unsigned int line ) {
+
+	/* Empty line buffer */
+	empty_line_buffer ( linebuf );
+	okx ( buffered_line ( linebuf ) == NULL, file, line );
+}
+#define linebuf_empty_ok( linebuf ) \
+	linebuf_empty_okx ( linebuf, __FILE__, __LINE__ )
+
+/**
+ * Report line buffer combined test result
+ *
+ * @v test		Line buffer test
+ * @v file		Test code file
+ * @v line		Test code line
+ */
+static void linebuf_okx ( struct linebuf_test *test, const char *file,
+			  unsigned int line ) {
+	struct line_buffer linebuf;
+
+	linebuf_init_okx ( &linebuf, file, line );
+	linebuf_consume_okx ( test, &linebuf, file, line );
+	linebuf_accumulated_okx ( test, &linebuf, file, line );
+	linebuf_empty_okx ( &linebuf, file, line );
+}
+#define linebuf_ok( test ) \
+	linebuf_okx ( test, __FILE__, __LINE__ )
+
+/**
+ * Perform line buffer self-tests
+ *
+ */
+static void linebuf_test_exec ( void ) {
+	struct line_buffer linebuf;
+
+	/* Basic tests */
+	linebuf_ok ( &simple );
+	linebuf_ok ( &mixed );
+
+	/* Split consumption test */
+	linebuf_init_ok ( &linebuf );
+	linebuf_consume_ok ( &split_1, &linebuf );
+	linebuf_consume_ok ( &split_2, &linebuf );
+	linebuf_consume_ok ( &split_3, &linebuf );
+	linebuf_consume_ok ( &split_4, &linebuf );
+	linebuf_consume_ok ( &split_5, &linebuf );
+	linebuf_consume_ok ( &split_6, &linebuf );
+	linebuf_empty_ok ( &linebuf );
+
+	/* Embedded NULs */
+	linebuf_ok ( &embedded_nuls );
+}
+
+/** Line buffer self-test */
+struct self_test linebuf_test __self_test = {
+	.name = "linebuf",
+	.exec = linebuf_test_exec,
+};
diff --git a/src/tests/tests.c b/src/tests/tests.c
index 0e6afee6..54ce8667 100644
--- a/src/tests/tests.c
+++ b/src/tests/tests.c
@@ -66,3 +66,4 @@ REQUIRE_OBJECT ( uri_test );
 REQUIRE_OBJECT ( profile_test );
 REQUIRE_OBJECT ( setjmp_test );
 REQUIRE_OBJECT ( pccrc_test );
+REQUIRE_OBJECT ( linebuf_test );