diff --git a/git-compat-util.h b/git-compat-util.h
index 4764087d85..0f856747e5 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -123,11 +123,17 @@ extern char *gitstrcasestr(const char *haystack, const char *needle);
 extern size_t gitstrlcpy(char *, const char *, size_t);
 #endif
 
+extern void release_pack_memory(size_t);
+
 static inline char* xstrdup(const char *str)
 {
 	char *ret = strdup(str);
-	if (!ret)
-		die("Out of memory, strdup failed");
+	if (!ret) {
+		release_pack_memory(strlen(str) + 1);
+		ret = strdup(str);
+		if (!ret)
+			die("Out of memory, strdup failed");
+	}
 	return ret;
 }
 
@@ -136,8 +142,14 @@ static inline void *xmalloc(size_t size)
 	void *ret = malloc(size);
 	if (!ret && !size)
 		ret = malloc(1);
-	if (!ret)
-		die("Out of memory, malloc failed");
+	if (!ret) {
+		release_pack_memory(size);
+		ret = malloc(size);
+		if (!ret && !size)
+			ret = malloc(1);
+		if (!ret)
+			die("Out of memory, malloc failed");
+	}
 #ifdef XMALLOC_POISON
 	memset(ret, 0xA5, size);
 #endif
@@ -149,8 +161,14 @@ static inline void *xrealloc(void *ptr, size_t size)
 	void *ret = realloc(ptr, size);
 	if (!ret && !size)
 		ret = realloc(ptr, 1);
-	if (!ret)
-		die("Out of memory, realloc failed");
+	if (!ret) {
+		release_pack_memory(size);
+		ret = realloc(ptr, size);
+		if (!ret && !size)
+			ret = realloc(ptr, 1);
+		if (!ret)
+			die("Out of memory, realloc failed");
+	}
 	return ret;
 }
 
@@ -159,8 +177,14 @@ static inline void *xcalloc(size_t nmemb, size_t size)
 	void *ret = calloc(nmemb, size);
 	if (!ret && (!nmemb || !size))
 		ret = calloc(1, 1);
-	if (!ret)
-		die("Out of memory, calloc failed");
+	if (!ret) {
+		release_pack_memory(nmemb * size);
+		ret = calloc(nmemb, size);
+		if (!ret && (!nmemb || !size))
+			ret = calloc(1, 1);
+		if (!ret)
+			die("Out of memory, calloc failed");
+	}
 	return ret;
 }
 
diff --git a/sha1_file.c b/sha1_file.c
index 8de8ce0a72..fb1032b0fd 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -522,6 +522,13 @@ static int unuse_one_window(struct packed_git *current)
 	return 0;
 }
 
+void release_pack_memory(size_t need)
+{
+	size_t cur = pack_mapped;
+	while (need >= (cur - pack_mapped) && unuse_one_window(NULL))
+		; /* nothing */
+}
+
 void unuse_pack(struct pack_window **w_cursor)
 {
 	struct pack_window *w = *w_cursor;