diff --git a/compat/mingw.c b/compat/mingw.c
index 2dce8c81e3..4cfa7d3ce4 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -2233,6 +2233,18 @@ void mingw_startup()
 			environ[i] = xstrdup(to_free + 6);
 			free(to_free);
 		}
+		if (starts_with(environ[i], "TMP=")) {
+			/*
+			 * Convert all dir separators to forward slashes,
+			 * to help shell commands called from the Git
+			 * executable (by not mistaking the dir separators
+			 * for escape characters.
+			 */
+			char *p;
+			for (p = environ[i]; *p; p++)
+				if (*p == '\\')
+					*p = '/';
+		}
 	}
 	environ[i] = NULL;
 	free(buffer);