diff --git a/src/blob.c b/src/blob.c
index ab7dec67f..30d5b705b 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -334,7 +334,8 @@ int git_blob_is_binary(const git_blob *blob)
 	assert(blob);
 
 	content.ptr   = blob->odb_object->buffer;
-	content.size  = min(blob->odb_object->cached.size, 4000);
+	content.size  =
+		min(blob->odb_object->cached.size, GIT_FILTER_BYTES_TO_CHECK_NUL);
 	content.asize = 0;
 
 	return git_buf_text_is_binary(&content);
diff --git a/src/diff_driver.c b/src/diff_driver.c
index dc8e79e25..c3c5f365b 100644
--- a/src/diff_driver.c
+++ b/src/diff_driver.c
@@ -397,7 +397,11 @@ void git_diff_driver_update_options(
 int git_diff_driver_content_is_binary(
 	git_diff_driver *driver, const char *content, size_t content_len)
 {
-	const git_buf search = { (char *)content, 0, min(content_len, 4000) };
+	git_buf search;
+
+	search.ptr   = (char *)content;
+	search.size  = min(content_len, GIT_FILTER_BYTES_TO_CHECK_NUL);
+	search.asize = 0;
 
 	GIT_UNUSED(driver);
 
diff --git a/src/filter.h b/src/filter.h
index d0ace0f9a..5a366108b 100644
--- a/src/filter.h
+++ b/src/filter.h
@@ -10,6 +10,10 @@
 #include "common.h"
 #include "git2/filter.h"
 
+/* Amount of file to examine for NUL byte when checking binary-ness */
+#define GIT_FILTER_BYTES_TO_CHECK_NUL 8000
+
+/* Possible CRLF values */
 typedef enum {
 	GIT_CRLF_GUESS = -1,
 	GIT_CRLF_BINARY = 0,