diff --git a/builtin/merge-tree.c b/builtin/merge-tree.c
index f8023bae1e..f32941fdab 100644
--- a/builtin/merge-tree.c
+++ b/builtin/merge-tree.c
@@ -76,7 +76,7 @@ static void *result(struct merge_list *entry, unsigned long *size)
 	their = NULL;
 	if (entry)
 		their = entry->blob;
-	return merge_blobs(path, base, our, their, size);
+	return merge_blobs(&the_index, path, base, our, their, size);
 }
 
 static void *origin(struct merge_list *entry, unsigned long *size)
diff --git a/merge-blobs.c b/merge-blobs.c
index 668fb2e05d..ee0a0e90c9 100644
--- a/merge-blobs.c
+++ b/merge-blobs.c
@@ -29,7 +29,12 @@ static void free_mmfile(mmfile_t *f)
 	free(f->ptr);
 }
 
-static void *three_way_filemerge(const char *path, mmfile_t *base, mmfile_t *our, mmfile_t *their, unsigned long *size)
+static void *three_way_filemerge(struct index_state *istate,
+				 const char *path,
+				 mmfile_t *base,
+				 mmfile_t *our,
+				 mmfile_t *their,
+				 unsigned long *size)
 {
 	int merge_status;
 	mmbuffer_t res;
@@ -42,7 +47,7 @@ static void *three_way_filemerge(const char *path, mmfile_t *base, mmfile_t *our
 	 */
 	merge_status = ll_merge(&res, path, base, NULL,
 				our, ".our", their, ".their",
-				&the_index, NULL);
+				istate, NULL);
 	if (merge_status < 0)
 		return NULL;
 
@@ -50,7 +55,9 @@ static void *three_way_filemerge(const char *path, mmfile_t *base, mmfile_t *our
 	return res.ptr;
 }
 
-void *merge_blobs(const char *path, struct blob *base, struct blob *our, struct blob *their, unsigned long *size)
+void *merge_blobs(struct index_state *istate, const char *path,
+		  struct blob *base, struct blob *our,
+		  struct blob *their, unsigned long *size)
 {
 	void *res = NULL;
 	mmfile_t f1, f2, common;
@@ -83,7 +90,7 @@ void *merge_blobs(const char *path, struct blob *base, struct blob *our, struct
 		common.ptr = xstrdup("");
 		common.size = 0;
 	}
-	res = three_way_filemerge(path, &common, &f1, &f2, size);
+	res = three_way_filemerge(istate, path, &common, &f1, &f2, size);
 	free_mmfile(&common);
 out_free_f2_f1:
 	free_mmfile(&f2);
diff --git a/merge-blobs.h b/merge-blobs.h
index 62b569e472..cc31038b80 100644
--- a/merge-blobs.h
+++ b/merge-blobs.h
@@ -1,8 +1,11 @@
 #ifndef MERGE_BLOBS_H
 #define MERGE_BLOBS_H
 
-#include "blob.h"
+struct blob;
+struct index_state;
 
-extern void *merge_blobs(const char *, struct blob *, struct blob *, struct blob *, unsigned long *);
+extern void *merge_blobs(struct index_state *, const char *,
+			 struct blob *, struct blob *,
+			 struct blob *, unsigned long *);
 
 #endif /* MERGE_BLOBS_H */