diff --git a/src/network/state.c b/src/network/state.c
index b5e4f098..910274c5 100644
--- a/src/network/state.c
+++ b/src/network/state.c
@@ -70,6 +70,7 @@ static const struct s_msg_dsc msg_dsc[] = {
 
 	{S_HTTP_ERROR,		N_("Bad HTTP response")},
 	{S_HTTP_204,		N_("No content")},
+	{S_HTTP_UPLOAD_RESIZED, N_("File was resized during upload")},
 
 	{S_FILE_TYPE,		N_("Unknown file type")},
 	{S_FILE_ERROR,		N_("Error opening file")},
diff --git a/src/network/state.h b/src/network/state.h
index e5e443a6..4583241b 100644
--- a/src/network/state.h
+++ b/src/network/state.h
@@ -72,6 +72,7 @@ enum connection_state {
 
 	S_HTTP_ERROR		= -100100,
 	S_HTTP_204		= -100101,
+	S_HTTP_UPLOAD_RESIZED   = -100102,
 
 	S_FILE_TYPE		= -100200,
 	S_FILE_ERROR		= -100201,
diff --git a/src/protocol/http/post.c b/src/protocol/http/post.c
index b4be5bc1..e8961916 100644
--- a/src/protocol/http/post.c
+++ b/src/protocol/http/post.c
@@ -35,6 +35,7 @@ init_http_post(struct http_post *http_post)
 	http_post->post_fd = -1;
 	http_post->file_index = 0;
 	http_post->file_count = 0;
+	http_post->file_read = 0;
 	http_post->files = NULL;
 }
 
@@ -54,6 +55,7 @@ done_http_post(struct http_post *http_post)
 	}
 	http_post->file_index = 0;
 	http_post->file_count = 0;
+	http_post->file_read = 0;
 	mem_free_set(&http_post->files, NULL);
 }
 
@@ -170,6 +172,7 @@ read_http_post_inline(struct http_post *http_post,
 		return total;
 	}
 
+	http_post->file_read = 0;
 	end = strchr(post + 1, FILE_CHAR);
 	assert(end);
 	*end = '\0';
@@ -199,6 +202,8 @@ read_http_post_fd(struct http_post *http_post,
 		  unsigned char buffer[], int max,
 		  enum connection_state *error)
 {
+	const struct http_post_file *const file
+		= &http_post->files[http_post->file_index];
 	int ret;
 
 	/* safe_read() would set errno = EBADF anyway, but check this
@@ -213,18 +218,42 @@ read_http_post_fd(struct http_post *http_post,
 		close(http_post->post_fd);
 		http_post->post_fd = -1;
 		http_post->file_index++;
+		/* http_post->file_read is used below so don't clear it here.
+		 * It will be cleared when the next file is opened.  */
 
-		if (ret == 0) {
+		if (ret == -1) {
+			*error = -errno_from_read;
+			return -1;
+		} else if (http_post->file_read != file->size) {
+			/* ELinks already sent a Content-Length header
+			 * based on the size of this file, but the
+			 * file has since been shrunk.  Abort the
+			 * connection because ELinks can no longer get
+			 * enough data to fill the Content-Length.
+			 * (Well, it could pad with zeroes, but that
+			 * would be just weird.)  */
+			*error = S_HTTP_UPLOAD_RESIZED;
+			return -1;
+		} else {
 			/* The upload file ended but there may still
 			 * be more data in uri.post.  If not,
 			 * read_http_post_inline() will return 0 to
 			 * indicate the final end of file.  */
 			return -2;
-		} else {
-			*error = -errno_from_read;
-			return -1;
 		}
 	}
+
+	http_post->file_read += ret;
+	if (http_post->file_read > file->size) {
+		/* ELinks already sent a Content-Length header based
+		 * on the size of this file, but the file has since
+		 * been extended.  Abort the connection because ELinks
+		 * can no longer fit the entire file in the original
+		 * Content-Length.  */
+		*error = S_HTTP_UPLOAD_RESIZED;
+		return -1;
+	}
+
 	return ret;
 }
 
diff --git a/src/protocol/http/post.h b/src/protocol/http/post.h
index 2fb79464..f17349d9 100644
--- a/src/protocol/http/post.h
+++ b/src/protocol/http/post.h
@@ -38,9 +38,14 @@ struct http_post {
 	 * be read next (when post_fd == -1).  */
 	size_t file_index;
 
-	/** Number of elements in the #files array.  */
+	/** Number of files to be uploaded, i.e. the number of
+	 * elements in the #files array.  */
 	size_t file_count;
 
+	/** Number of bytes read from the current file so far.
+	 * The value makes sense only when post_fd != -1.  */
+	off_t file_read;
+
 	/** Array of information about files to be uploaded.  */
 	struct http_post_file *files;
 };