diff --git a/os/log.c b/os/log.c
index df025fbca..e4e9e8b9d 100644
--- a/os/log.c
+++ b/os/log.c
@@ -450,6 +450,9 @@ pnprintf(char *string, size_t size, const char *f, va_list args)
                     string[s_idx++] = number[i];
             }
             break;
+        case '%':
+            string[s_idx++] = '%';
+            break;
         default:
             va_arg(args, char*);
             string[s_idx++] = '%';
diff --git a/test/signal-logging.c b/test/signal-logging.c
index 9038cf81f..65baa456f 100644
--- a/test/signal-logging.c
+++ b/test/signal-logging.c
@@ -196,6 +196,11 @@ static void logging_format(void)
     read_log_msg(logmsg);
     assert(strcmp(logmsg, "(EE) %s %d %u %% %p %i\n") == 0);
 
+    /* literal % */
+    LogMessageVerbSigSafe(X_ERROR, -1, "test %%\n");
+    read_log_msg(logmsg);
+    assert(strcmp(logmsg, "(EE) test %\n") == 0);
+
     /* string substitution */
     LogMessageVerbSigSafe(X_ERROR, -1, "%s\n", "substituted string");
     read_log_msg(logmsg);