diff --git a/builtin/grep.c b/builtin/grep.c
index 9e34a820ad..d85cbabea6 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -26,6 +26,8 @@
 #include "object-store.h"
 #include "packfile.h"
 
+static const char *grep_prefix;
+
 static char const * const grep_usage[] = {
 	N_("git grep [<options>] [-e] <pattern> [<rev>...] [[--] <path>...]"),
 	NULL
@@ -315,11 +317,11 @@ static void grep_source_name(struct grep_opt *opt, const char *filename,
 	strbuf_reset(out);
 
 	if (opt->null_following_name) {
-		if (opt->relative && opt->prefix_length) {
+		if (opt->relative && grep_prefix) {
 			struct strbuf rel_buf = STRBUF_INIT;
 			const char *rel_name =
 				relative_path(filename + tree_name_len,
-					      opt->prefix, &rel_buf);
+					      grep_prefix, &rel_buf);
 
 			if (tree_name_len)
 				strbuf_add(out, filename, tree_name_len);
@@ -332,8 +334,8 @@ static void grep_source_name(struct grep_opt *opt, const char *filename,
 		return;
 	}
 
-	if (opt->relative && opt->prefix_length)
-		quote_path(filename + tree_name_len, opt->prefix, out, 0);
+	if (opt->relative && grep_prefix)
+		quote_path(filename + tree_name_len, grep_prefix, out, 0);
 	else
 		quote_c_style(filename + tree_name_len, out, NULL, 0);
 
@@ -962,9 +964,10 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 			   PARSE_OPT_NOCOMPLETE),
 		OPT_END()
 	};
+	grep_prefix = prefix;
 
 	git_config(grep_cmd_config, NULL);
-	grep_init(&opt, the_repository, prefix);
+	grep_init(&opt, the_repository);
 
 	/*
 	 * If there is no -- then the paths must exist in the working
diff --git a/builtin/ls-tree.c b/builtin/ls-tree.c
index 3a442631c7..6cb554cbb0 100644
--- a/builtin/ls-tree.c
+++ b/builtin/ls-tree.c
@@ -150,7 +150,7 @@ int cmd_ls_tree(int argc, const char **argv, const char *prefix)
 
 	git_config(git_default_config, NULL);
 	ls_tree_prefix = prefix;
-	if (prefix && *prefix)
+	if (prefix)
 		chomp_prefix = strlen(prefix);
 
 	argc = parse_options(argc, argv, prefix, ls_tree_options,
diff --git a/git.c b/git.c
index edda922ce6..9d257e092d 100644
--- a/git.c
+++ b/git.c
@@ -436,6 +436,7 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
 	} else {
 		prefix = NULL;
 	}
+	assert(!prefix || *prefix);
 	precompose_argv_prefix(argc, argv, NULL);
 	if (use_pager == -1 && run_setup &&
 		!(p->option & DELAY_PAGER_CONFIG))
diff --git a/grep.c b/grep.c
index 7bb0360869..8421dc5548 100644
--- a/grep.c
+++ b/grep.c
@@ -139,13 +139,11 @@ int grep_config(const char *var, const char *value, void *cb)
  * default values from the template we read the configuration
  * information in an earlier call to git_config(grep_config).
  */
-void grep_init(struct grep_opt *opt, struct repository *repo, const char *prefix)
+void grep_init(struct grep_opt *opt, struct repository *repo)
 {
 	*opt = grep_defaults;
 
 	opt->repo = repo;
-	opt->prefix = prefix;
-	opt->prefix_length = (prefix && *prefix) ? strlen(prefix) : 0;
 	opt->pattern_tail = &opt->pattern_list;
 	opt->header_tail = &opt->header_list;
 }
diff --git a/grep.h b/grep.h
index 400172676a..23a2a41d2c 100644
--- a/grep.h
+++ b/grep.h
@@ -134,8 +134,6 @@ struct grep_opt {
 	 */
 	struct repository *repo;
 
-	const char *prefix;
-	int prefix_length;
 	int linenum;
 	int columnnum;
 	int invert;
@@ -182,7 +180,7 @@ struct grep_opt {
 };
 
 int grep_config(const char *var, const char *value, void *);
-void grep_init(struct grep_opt *, struct repository *repo, const char *prefix);
+void grep_init(struct grep_opt *, struct repository *repo);
 void grep_commit_pattern_type(enum grep_pattern_type, struct grep_opt *opt);
 
 void append_grep_pat(struct grep_opt *opt, const char *pat, size_t patlen, const char *origin, int no, enum grep_pat_token t);
diff --git a/revision.c b/revision.c
index ad4286fbdd..d6e0e2b23b 100644
--- a/revision.c
+++ b/revision.c
@@ -1838,7 +1838,7 @@ void repo_init_revisions(struct repository *r,
 	revs->commit_format = CMIT_FMT_DEFAULT;
 	revs->expand_tabs_in_log_default = 8;
 
-	grep_init(&revs->grep_filter, revs->repo, prefix);
+	grep_init(&revs->grep_filter, revs->repo);
 	revs->grep_filter.status_only = 1;
 
 	repo_diff_setup(revs->repo, &revs->diffopt);