diff --git a/tests/unix/extra_coverage.py.exp b/tests/unix/extra_coverage.py.exp
index 4169938870..390ff1669d 100644
--- a/tests/unix/extra_coverage.py.exp
+++ b/tests/unix/extra_coverage.py.exp
@@ -11,6 +11,7 @@ false true
 2147483648
 80000000
 80000000
+abc
 # vstr
 tests
 sts
diff --git a/unix/coverage.c b/unix/coverage.c
index 09959525a0..8391cd08be 100644
--- a/unix/coverage.c
+++ b/unix/coverage.c
@@ -154,6 +154,7 @@ STATIC mp_obj_t extra_coverage(void) {
         mp_printf(&mp_plat_print, "%u\n", 0x80000000); // should print unsigned
         mp_printf(&mp_plat_print, "%x\n", 0x80000000); // should print unsigned
         mp_printf(&mp_plat_print, "%X\n", 0x80000000); // should print unsigned
+        mp_printf(&mp_plat_print, "abc\n%"); // string ends in middle of format specifier
     }
 
     // vstr