diff --git a/printbuf.c b/printbuf.c
index e9cde11..b02a363 100644
--- a/printbuf.c
+++ b/printbuf.c
@@ -13,6 +13,7 @@
 
 #include "config.h"
 
+#include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -68,9 +69,16 @@ static int printbuf_extend(struct printbuf *p, int min_size)
 	if (p->size >= min_size)
 		return 0;
 
-	new_size = p->size * 2;
-	if (new_size < min_size + 8)
-		new_size =  min_size + 8;
+	/* Prevent signed integer overflows with large buffers. */
+	if (min_size > INT_MAX - 8)
+		return -1;
+	if (p->size > INT_MAX / 2)
+		new_size = min_size + 8;
+	else {
+		new_size = p->size * 2;
+		if (new_size < min_size + 8)
+			new_size = min_size + 8;
+	}
 #ifdef PRINTBUF_DEBUG
 	MC_DEBUG("printbuf_memappend: realloc "
 	  "bpos=%d min_size=%d old_size=%d new_size=%d\n",
@@ -85,6 +93,9 @@ static int printbuf_extend(struct printbuf *p, int min_size)
 
 int printbuf_memappend(struct printbuf *p, const char *buf, int size)
 {
+	/* Prevent signed integer overflows with large buffers. */
+	if (size > INT_MAX - p->bpos - 1)
+		return -1;
 	if (p->size <= p->bpos + size + 1) {
 		if (printbuf_extend(p, p->bpos + size + 1) < 0)
 			return -1;
@@ -136,6 +147,9 @@ int printbuf_memset(struct printbuf *pb, int offset, int charvalue, int len)
 
 	if (offset == -1)
 		offset = pb->bpos;
+	/* Prevent signed integer overflows with large buffers. */
+	if (len > INT_MAX - offset)
+		return -1;
 	size_needed = offset + len;
 	if (pb->size < size_needed)
 	{