diff --git a/c/input/line_readers.c b/c/input/line_readers.c
index 9caaf7cd0..2f881bd1b 100644
--- a/c/input/line_readers.c
+++ b/c/input/line_readers.c
@@ -90,7 +90,7 @@ char* mlr_get_sline(FILE* fp, char* irs, int irslen) {
 }
 
 // ----------------------------------------------------------------
-int local_getdelim(char** restrict pline, size_t* restrict plinecap, int delimiter, FILE* restrict stream) {
+ssize_t local_getdelim(char** restrict pline, size_t* restrict plinecap, int delimiter, FILE* restrict stream) {
 	size_t linecap = INITIAL_SIZE;
 	char* restrict line = mlr_malloc_or_die(INITIAL_SIZE);
 	char* restrict p = line;
@@ -106,26 +106,32 @@ int local_getdelim(char** restrict pline, size_t* restrict plinecap, int delimit
 		}
 		c = mlr_arch_getc(stream);
 		if (c == delimiter) {
-			*(p++) = 0;
+			*(p++) = delimiter;
 			break;
 		} else if (c == EOF) {
 			if (p == line)
 				eof = TRUE;
-			*p = 0;
 			break;
 		} else {
 			*(p++) = c;
 		}
 	}
 
+	// xxx check length
+	size_t offset = p - line;
+	if (offset >= linecap) {
+		linecap = linecap + 1;
+		line = mlr_realloc_or_die(line, linecap);
+		p = line + offset;
+	}
+	p[1] = 0;
+
+	*pline = line;
+	*plinecap = linecap;
 	if (eof) {
-		free(line);
-		*pline = NULL;
-		*plinecap = 0;
+		**pline = 0;
 		return -1;
 	} else {
-		*pline = line;
-		*plinecap = linecap;
 		return p - line;
 	}
 }
diff --git a/c/input/line_readers.h b/c/input/line_readers.h
index d5f669621..12e61b4e0 100644
--- a/c/input/line_readers.h
+++ b/c/input/line_readers.h
@@ -22,6 +22,6 @@ char*  mlr_get_sline(FILE* input_stream, char* irs, int irslen);
 // getdelim is built-in on OSX and modern unix-like OSs. For MSYS2, we need to
 // roll our own. The function is exposed publicly here, rather than privately
 // inside mlr_arch.c, for unit-testing visibility.
-int local_getdelim(char** restrict pline, size_t* restrict plinecap, int delimiter, FILE* restrict stream);
+ssize_t local_getdelim(char** restrict pline, size_t* restrict plinecap, int delimiter, FILE* restrict stream);
 
 #endif // LINE_READERS_H
diff --git a/c/unit_test/test_line_readers.c b/c/unit_test/test_line_readers.c
index 3078249a4..fece80cf8 100644
--- a/c/unit_test/test_line_readers.c
+++ b/c/unit_test/test_line_readers.c
@@ -13,6 +13,8 @@ int tests_failed      = 0;
 int assertions_run    = 0;
 int assertions_failed = 0;
 
+typedef ssize_t getdelim_t(char** restrict pline, size_t* restrict plinecap, int delimiter, FILE* restrict stream);
+
 // ----------------------------------------------------------------
 static FILE* fopen_or_die(char* filename) {
 	FILE* fp = fopen(filename, "r");
@@ -24,20 +26,7 @@ static FILE* fopen_or_die(char* filename) {
 	return fp;
 }
 
-// ----------------------------------------------------------------
-// This tests our homemade getdelim replacement, for running on Windows which lacks getdelim.
-
-static char* test_local_getdelim() {
-
-	return NULL;
-}
-
-// ----------------------------------------------------------------
-// On unixish platforms this is testing the system getdelim() which is correct by definition.
-// (At least, we verify it's behaving as we expect.) On Windows, this tests our local_getdelim
-// which is a radundant test -- but again, it confirms behavior is as expected.
-
-static char* test_getdelim() {
+static char* test_getdelim_impl(getdelim_t* pgetdelim) {
 	char delimiter = '\n';
 	char* contents = NULL;
 	char* path = NULL;
@@ -54,7 +43,7 @@ static char* test_getdelim() {
 	// Read line
 	line = NULL;
 	linecap = 0;
-	rc = getdelim(&line, &linecap, delimiter, fp);
+	rc = (*pgetdelim)(&line, &linecap, delimiter, fp);
 	mu_assert_lf(rc == -1);
 	mu_assert_lf(streq(line, ""));
 	mu_assert_lf(linecap >= 1+strlen(contents));
@@ -62,7 +51,7 @@ static char* test_getdelim() {
 	// Read past EOF
 	line = NULL;
 	linecap = 0;
-	rc = getdelim(&line, &linecap, delimiter, fp);
+	rc = (*pgetdelim)(&line, &linecap, delimiter, fp);
 	mu_assert_lf(rc == -1);
 	mu_assert_lf(streq(line, ""));
 
@@ -78,7 +67,7 @@ static char* test_getdelim() {
 	// Read line
 	line = NULL;
 	linecap = 0;
-	rc = getdelim(&line, &linecap, delimiter, fp);
+	rc = (*pgetdelim)(&line, &linecap, delimiter, fp);
 	mu_assert_lf(rc == 1);
 	mu_assert_lf(streq(line, "\n"));
 	mu_assert_lf(linecap >= 1+strlen(contents));
@@ -86,7 +75,7 @@ static char* test_getdelim() {
 	// Read past EOF
 	line = NULL;
 	linecap = 0;
-	rc = getdelim(&line, &linecap, delimiter, fp);
+	rc = (*pgetdelim)(&line, &linecap, delimiter, fp);
 	mu_assert_lf(rc == -1);
 	mu_assert_lf(streq(line, ""));
 
@@ -102,7 +91,7 @@ static char* test_getdelim() {
 	// Read line
 	line = NULL;
 	linecap = 0;
-	rc = getdelim(&line, &linecap, delimiter, fp);
+	rc = (*pgetdelim)(&line, &linecap, delimiter, fp);
 	mu_assert_lf(rc == 2);
 	mu_assert_lf(streq(line, "\r\n"));
 	mu_assert_lf(linecap >= 1+strlen(contents));
@@ -110,7 +99,7 @@ static char* test_getdelim() {
 	// Read past EOF
 	line = NULL;
 	linecap = 0;
-	rc = getdelim(&line, &linecap, delimiter, fp);
+	rc = (*pgetdelim)(&line, &linecap, delimiter, fp);
 	mu_assert_lf(rc == -1);
 	mu_assert_lf(streq(line, ""));
 
@@ -121,10 +110,24 @@ static char* test_getdelim() {
 	return NULL;
 }
 
+// ----------------------------------------------------------------
+// On unixish platforms this is testing the system getdelim() which is correct by definition.
+// (At least, we verify it's behaving as we expect.) On Windows, this tests our local_getdelim
+// which is a radundant test -- but again, it confirms behavior is as expected.
+static char* test_getdelim() {
+	return test_getdelim_impl(&mlr_arch_getdelim);
+}
+
+// ----------------------------------------------------------------
+// This tests our homemade getdelim replacement, for running on Windows which lacks getdelim.
+static char* test_local_getdelim() {
+	return test_getdelim_impl(&local_getdelim);
+}
+
 // ================================================================
 static char * run_all_tests() {
-	mu_run_test(test_local_getdelim);
 	mu_run_test(test_getdelim);
+	mu_run_test(test_local_getdelim);
 	return 0;
 }